Free Engineering Calculator | Multi-Discipline Tool
Free engineering calculator puts 35 professional-grade tools on one page: beam strength, RC beam, column buckling, bolt checks, HVAC cooling load, transformer sizing, pipe flow, heat exchangers, and a full unit converter.
Civil and structural engineers, electrical engineers, mechanical designers, HVAC technicians, and engineering students. Whether you're sizing a UB beam for a mezzanine, checking voltage drop on a 60 m cable run, calculating transformer short-circuit current, or estimating a room's cooling load, the answer is a few seconds away.
Engineering Calculator runs entirely in your browser. No data is sent to a server, no account is needed, and no ads interrupt your workflow. Bookmark the page and use it on-site, in the office, or offline.
Disclaimer: Results are for preliminary estimation only. Always verify critical designs against the applicable codes and a qualified engineer's review.
Free Engineering Calculator
35 tools with SFD/BMD charts, Compare A/B, projects, PDF & BoQ export.
Engineering Calculator — Complete User Guide
A free, browser-based toolkit for structural, electrical, mechanical, fluid, thermal, and HVAC engineers. 35 real tools, live SFD/BMD/deflection charts, Compare A/B, project saving, PDF and BoQ export — no login required.
1. What is the Engineering Calculator?
The Engineering Calculator is a single-page, offline-capable engineering toolkit that runs entirely in your browser. It bundles 35 discipline-specific calculators — beam analysis, RC design, footings, retaining walls, motor sizing, cable voltage drop, pipe flow, heat exchangers, cooling loads, pressure vessels, bolted joints, and more — behind one searchable interface.
Unlike most free online calculators, Engineering Calculator does more than produce a number. It draws the shear force diagram (SFD), bending moment diagram (BMD), and deflection curve for beam problems, lets you pin one design (A) and compare it against a revised design (B) side-by-side with a live delta column, stores your starred tools and inputs as named projects inside localStorage, and exports a clean BoQ CSV or PDF/PNG summary with the Engineering Calculator logo for client reports.
It runs entirely client-side. There is no server, no sign-up, and no data ever leaves your device — usable on site, on a plane, or behind a corporate firewall.
2. How the toolkit is structured — visual overview
The diagram below shows how the seven tool categories feed into shared features (charts, favourites, projects, exports). On desktop the SVG scales up to 900 px wide; on mobile it shrinks fluidly to the container width.
3. Step-by-step: how to use the calculator
The workflow is the same for all 35 tools. Follow these seven steps once and you can drive any calculator in the toolkit.
Step 1 — Pick a tool from a category
At the top of the calculator you will see a row of category tabs: StructuralElectricalMechanicalFluidThermalHVACOther. Click a category to reveal the tools inside it. You can also type a keyword — beam, bolt, slab, motor — into the search box at the top to jump directly to a tool.
Tip: if you use a tool often, click the small ☆ star at the top-right of its tab. The tool becomes a favourite, floats to the top of its category, and appears in a dedicated ★ Favourites category.
Step 2 — Understand the input fields
Every field has a label, a unit in parentheses, and — where relevant — a hint below it. The table below explains the field types you will see.
| Field type | What it means | Example |
|---|---|---|
| Numeric input | A number in the unit shown. Use decimals, not fractions. Do not type the unit. | 300 for a 300 mm beam depth |
| Dropdown (material) | Preset values for E (elastic modulus), density, and yield strength. Pick the closest match. | Mild steel A36 · E = 200 GPa · fy = 250 MPa |
| Dropdown (section) | Standard profile shapes — I-beam, channel, tee, angle, rectangle, tube, pipe, round. | I-beam for UB/UC sections |
| Dropdown (support) | Boundary condition for beam problems. Governs moment, shear, and deflection formulas. | Simply supported · Cantilever · Fixed both ends |
| Safety factor | Divisor applied to yield strength to obtain allowable stress. Default 1.5. | 1.5 for general steelwork |
Step 3 — Enter your values and press Calculate
Fill in the fields top to bottom. Fields marked with a light hint below them show the expected range. When you are ready, click the orange Calculate button. You can also press Enter inside any numeric field to calculate immediately.
Input validation
If a value is missing or invalid, a red error message appears above the result panel telling you exactly which field to fix. Common messages and their meaning:
- “Enter h, b, web t, flange tf.” — one or more section dimensions are blank.
- “Thickness too large.” — the flange or wall thickness you entered exceeds half the depth; the section is geometrically impossible.
- “Enter at least two positive values.” — Ohm's law needs any two of V, I, R, or P.
- “Wall too thick.” — for pipe/tube, the wall thickness is more than half the outer diameter.
- “Orifice diameter must be smaller than pipe diameter.” — β = d/D must be < 1.
Step 4 — Read the results panel
Each result row has three parts:
| Part | Meaning |
|---|---|
| Label (left) | What is being reported (e.g. Bending stress). |
| Value (right, monospace) | The numeric answer, rounded to a sensible number of decimals for that quantity. |
| Unit (small, grey) | Unit of the value (MPa, kN·m, mm, %…). |
Colour coding:
| Colour | Meaning | Action |
|---|---|---|
| Green value | OK / PASS — the check is satisfied. | Proceed. |
| Amber value | Warning — acceptable but outside recommended limits (e.g. very high span/depth ratio). | Review inputs or consider upsizing. |
| Red value | FAIL — the design does not meet the limit state. | Change section, material, or geometry. |
| Black value | An informational quantity — no pass/fail judgement. | Reference. |
Step 5 — View the SFD, BMD, and deflection charts (Beam tool)
For the Beam tool, three canvas charts are drawn below the results: Shear Force Diagram (kN), Bending Moment Diagram (kN·m), and Deflection (mm). The curve is computed from the exact closed-form solution for the selected support condition, including cantilever and fixed-end cases where the boundary condition matters. See Section 6 for details.
Step 6 — Pin a result (A) and iterate (B) with Compare A/B
After calculating, click 📌 Pin A. The current result is frozen as A, and a comparison table appears below the results. Now change any input — section depth, material, span — and click Calculate again. Column B updates with the new result, and a Δ B−A column shows the change for every row. Rows that changed are tinted orange. Click ↺ Clear A/B to remove the comparison. See Section 7 for the full workflow.
Step 7 — Save, share, and export
- Save as a named project: star the tools you are using, fill in your inputs, type a name into the Project field at the top of the calculator and click Save. Return later, pick the project from the dropdown, click Load.
- Share a link: click Copy share link under any tool. Every input is encoded into the URL hash so a colleague opens exactly the same calculation.
- Print a clean summary: click Print summary to build a print-friendly page showing only inputs, results, and formulas. Use your browser’s Save as PDF to archive.
- Export PDF and BoQ CSV: header PDF produces a PNG of all calculated tools with logo and date. 📊 BoQ CSV exports every result row from starred tools for Excel.
4. Global tools
⭐ Favourites
Click the ☆ on any tab. It turns gold and the tab floats to the top of its category. A new ★ Favourites category appears in the category bar showing only starred tools. Click the star again to remove. Clear favourites in the footer wipes the whole list.
🌙 Dark mode
Click 🌙 in the header (or Toggle dark mode in the footer). The setting is remembered on your device. First-time visitors get the theme their operating system prefers.
🔍 Search
Type any part of a name: beam, bolt, slab, ohm. The tab list filters live. Press Clear to go back to the normal category view.
📁 Projects
- Star the tools you want in this project (e.g. Beam, Column, Footing).
- Fill in their inputs.
- Type a name in the New project name box.
- Click Save. The name appears in the dropdown.
- Later, select it and click Load to restore the starred tools and every input value.
- Delete removes the selected project permanently.
📄 PDF export
Click PDF in the header to export every calculated tool as a single PNG page with the Engineering Calculator logo and a clean two-column layout. A file named Engineering Calculator_summary.png downloads.
📊 BoQ CSV
Click 📊 BoQ CSV. Every row of every starred tool’s results is written to Engineering Calculator_BoQ.csv with four columns: Tool, Label, Value, Unit. Open in Excel/Sheets for quantities, costing, or client submission.
Print ⭐ (header) or Print all starred (footer) → clean printable layout showing inputs, results, and formulas for every starred tool. Print summary on a single tool prints just that one. Ctrl+P anywhere auto-generates a print root for everything currently calculated.
🔗 Share link
Click Copy share link. Every input value is encoded into the URL. Send that URL to a colleague — it opens on the exact same calculation.
5. Understanding the results panel
Each result row has three parts:
| Part | Meaning |
|---|---|
| Label (left) | What is being reported. |
| Value (right, monospace) | The numeric answer. |
| Unit (small, grey) | Unit of the value (MPa, kN·m, mm, %…). |
Colour coding
| Colour | Meaning |
|---|---|
| Green value | OK / PASS — the check is satisfied. |
| Amber value | Warning — acceptable but outside recommended limits. |
| Red value | FAIL — the design does not meet the limit state. |
| Black value | An informational quantity — no pass/fail judgement. |
6. SFD / BMD / deflection charts explained
Only the Beam tool shows charts. After a successful calculation, three panels appear side by side:
| Chart | What it shows |
|---|---|
| SFD — Shear Force Diagram | Internal shear force V(x) along the span, in kN. Sign convention: positive upward on the left support. |
| BMD — Bending Moment Diagram | Internal bending moment M(x) along the span, in kN·m. The peak is where the beam is most stressed. |
| Deflection | Downward displacement δ(x) of the beam, in mm. For cantilevers the maximum is at the free end; for simply supported beams it is at mid-span. |
All three use the exact analytical solution — not a numerical approximation. Cantilever and fixed-end boundary conditions are handled with the correct closed-form equations, so the deflection curve starts at zero at the fixed support and slopes correctly at the free end.
Read the charts together with the numbers:
- The peak of the BMD is where the bending stress is highest — check that the section modulus in that region is adequate.
- The slope of the BMD equals the shear force; a sharp jump indicates a point load.
- The maximum deflection is usually at midspan for simply supported cases, but shifts toward the free end for cantilevers.
7. Compare A/B — iterate a design in seconds
- Enter your first design, click Calculate.
- Click 📌 Pin A. That result is now frozen as the baseline.
- Change any input — section size, span, load, support type.
- Click Calculate again. The Compare A vs B table appears below the results.
| Column | Meaning |
|---|---|
| A (pinned) | Every result row from design A, exactly as it was when you pinned it. |
| B (current) | Every result row from the new calculation. |
| Δ B−A | The change. Positive means B is larger; negative means smaller. The unit is carried over from the row. |
Rows where the value changed are tinted orange so you can scan the delta instantly. Click ↺ Clear A/B to remove the baseline and start a fresh comparison.
8. Worked example — simply supported steel beam
Let’s walk through a complete beam check with real values so you can see exactly what each field does and what the results mean.
Inputs
| Field | Value | Why |
|---|---|---|
| Material | Mild steel A36 | E = 200 GPa, fy = 250 MPa — most common structural steel. |
| Section profile | I-beam | Rolled universal beam shape. |
| Support and load | Simply supported, center point load | Typical floor beam with a midspan point load. |
| Height h | 400 mm | Depth of the section. |
| Width b | 180 mm | Flange width. |
| Web thickness tw | 8 mm | Web plate thickness. |
| Flange thickness tf | 12 mm | Flange plate thickness. |
| Span L | 6 m | Clear span between supports. |
| Load P | 80 kN | Central point load. |
| Safety factor | 1.5 | Applied to fy to give allowable stress. |
What the calculator returns
| Result | Approximate value | Interpretation |
|---|---|---|
| Cross-section area | ~7,500 mm² | Section area for weight and shear checks. |
| Moment of inertia I | ~22,000 cm⁴ | Bending stiffness for deflection. |
| Section modulus Z | ~1,100 cm³ | For bending stress = M / Z. |
| Max bending moment | 120 kN·m | M = PL/4 = 80 × 6 / 4. |
| Max shear force | 40 kN | V = P/2 at each support. |
| Bending stress | ~109 MPa | σ = M / Z — under allowable 167 MPa (fy/1.5). |
| Max deflection | ~10 mm | δ = PL³/(48EI). Span/600 limit = 10 mm → borderline. |
| Strength check | PASS | Utilisation ~65%. |
Iterate with Compare A/B
Pin A at these values. Now change h from 400 to 450 mm and calculate again. Column B shows the new deflection (roughly 7 mm) and the Δ B−A column shows a reduction of about −3 mm. You now have a documented comparison for your design file.
9. Structural tools — field-by-field reference
Structural 9.1 Beam
Strength, shear, deflection, weight and diagrams for the seven most common beam/support combinations.
| Field | Unit | What to enter |
|---|---|---|
| Material | — | Pick a preset. The first number inside the value (E in GPa) is used for deflection; the second is density for weight; the third is yield strength for the pass/fail check. |
| Section profile | — | I-beam, Channel, T-section, Angle, Solid rectangle, Rectangular tube, Circular pipe or Solid round bar. The tool computes area, second moment of inertia I, distance to extreme fibre c, and shear area Aw from the geometry you enter below. |
| Support and load type | — | Simply supported (point or uniform), Cantilever (point or uniform), Two-equal-span continuous (uniform), Fixed-fixed (point or uniform). This choice decides which M(x), V(x) and δ(x) formulas are used and whether the deflection limit is L/360 or L/180. |
| Height or diameter h | mm | Overall depth for I/Channel/T/Angle/Rect/Tube/Pipe; diameter for Round bar. |
| Width / flange b | mm | Flange width for I/Channel/T; second leg for Angle; width for Rect/Tube. Not used for Pipe or Round bar. |
| Web / wall thickness t | mm | Web thickness for I/Channel; stem thickness for T; leg thickness for Angle; wall for Tube; wall for Pipe. Not used for Rect or Round. |
| Flange thickness tf | mm | Only used for I-beam, Channel and T-section. |
| Span length L | m | Clear span between supports, or cantilever length. |
| Load | kN or kN/m | Enter kN if the support type is a point-load case; enter kN/m if uniform load. The tool reads this value either way — it applies it as P (point) or w (uniform) depending on the support type. |
| Safety factor | — | Divides the material yield strength to get the allowable stress. Default 1.5. |
Key results: Section area, Moment of inertia I, Section modulus Z, Beam weight and weight per metre, Max bending moment, Max shear, Bending stress σ, Shear stress τ, Allowable stress, Stress utilization %, Max deflection δ, Span/deflection ratio, PASS/FAIL.
Structural 9.2 Section DB
Ready-made properties for 20 common UK UB and UC sections.
| Field | Unit | What to enter |
|---|---|---|
| Section | — | Pick from the dropdown list of designations. |
| Show | — | Full property list adds the approximate cross-sectional area; Key values only hides it. |
How to use it with the Beam tool: look up Depth h, Width b, Web thickness tw and Flange thickness tf here, then copy them into the Beam inputs with the profile set to I-beam.
Structural 9.3 Multi-Load Beam
Combined loads on a simply supported beam: uniform + triangular + up to four point loads. Solves for reactions, peak moment and its location, and midspan deflection numerically.
| Field | Unit | What to enter |
|---|---|---|
| Span L | m | Beam span. |
| Uniform w | kN/m | Constant load over the whole span (self weight plus finishes). Enter 0 if none. |
| Triangular peak | kN/m | Triangular load that is zero at the left support and rises to this value at the right support. Enter 0 for none. |
| Point P₁…P₄ | kN | Point load magnitudes. Leave 0 to skip. |
| Position x₁…x₄ | m | Distance from the left support to each point load. |
| EI | kN·m² | Flexural rigidity. E in kPa × I in m⁴. Example: steel E ≈ 200×10⁶ kPa, UB 305×165×40 I ≈ 8.5×10⁻⁵ m⁴ → EI ≈ 17,000 kN·m². |
Results: Reaction R₁, Reaction R₂, Max shear, Max bending moment and its position, midspan deflection, number of active point loads.
Structural 9.4 Load Combo
Governing factored load from Dead, Live, Wind and Snow per ASCE 7 (LRFD) or Eurocode ULS.
| Field | Unit | What to enter |
|---|---|---|
| Dead load D | kN/m | Self weight and permanent finishes. |
| Live load L | kN/m | Imposed / occupancy load. |
| Wind W | kN/m | Enter 0 if not applicable. |
| Snow S | kN/m | Enter 0 if not applicable. |
| Code | — | ASCE 7 LRFD or Eurocode ULS. The list of combinations changes with this choice. |
Result: every combination is listed and sorted from highest to lowest. The top row is highlighted green — that is the governing load case.
Structural 9.5 RC Beam
Singly or doubly reinforced rectangular concrete beam to a Eurocode-style approach.
| Field | Unit | What to enter |
|---|---|---|
| Width b | mm | Beam web width. |
| Overall depth h | mm | Total depth from top of concrete to bottom of beam. |
| Cover | mm | Clear cover to the outer edge of the tension reinforcement. |
| Design moment M | kN·m | Factored (ULS) bending moment at the section being designed. |
| Concrete fck | MPa | Characteristic cylinder strength. 25–40 MPa typical. |
| Steel fy | MPa | Characteristic yield strength. 500 MPa typical for UK/EU rebar. |
| Bar diameter | mm | Nominal bar size — used only to convert required area into a number of bars. |
Results: Effective depth d, K factor, lever arm z, Required As, As,min, As,max, number of bars, steel ratio %, singly/doubly reinforced flag, Provided As, PASS/FAIL.
How to read the check: if K exceeds Kbal ≈ 0.167, the tool automatically switches to doubly reinforced and reports the additional compression steel As′.
Structural 9.6 Slab
One-way reinforced concrete slab — required steel area and bar spacing.
| Field | Unit | What to enter |
|---|---|---|
| Span L | m | Effective span in the short direction (one-way action). |
| Slab depth D | mm | Overall slab thickness. |
| Live load | kN/m² | Imposed load per square metre. |
| Additional dead load | kN/m² | Floor finishes, services — excluding the slab’s own self weight (added automatically at 25 kN/m³). |
| fy | MPa | Rebar yield strength. |
| fck | MPa | Concrete strength. |
| Cover | mm | Nominal cover to reinforcement. |
| Bar dia | mm | 8 / 10 / 12 / 16 mm. |
Results: Self weight, Design load wu, Moment M per metre width, Effective depth d, Required As, As,min, recommended centre-to-centre bar spacing (capped at 300 mm).
Structural 9.7 Footing
Pad footing sizing under a column load with optional moment.
| Field | Unit | What to enter |
|---|---|---|
| Column load | kN | Total service axial load on the footing. |
| Moment | kN·m | Applied moment at the base of the column. Enter 0 if none. |
| Allowable soil | kPa | Safe bearing capacity from a geotechnical report. |
| Length L | m | Footing dimension in the direction of bending. |
| Width B | m | Footing dimension perpendicular to bending. |
| Thickness | mm | Trial footing thickness (used to estimate self weight at 24 kN/m³). |
| fck | MPa | Concrete strength for reporting. |
Results: Actual area, Required area, Average pressure, Max pressure, Min pressure, Self weight, PASS/FAIL. If min pressure is negative, uplift is occurring and the footing is too small.
Structural 9.8 Retaining Wall
Rankine active pressure and stability check for a cantilever retaining wall.
| Field | Unit | What to enter |
|---|---|---|
| Wall height H | m | Height of retained soil. |
| Soil γ | kN/m³ | Bulk unit weight of the backfill. Typically 18–20 kN/m³. |
| Friction φ | ° | Angle of internal friction. 30° for typical granular fill. |
| Surcharge q | kN/m² | Uniform surcharge behind the wall. Enter 0 if none. |
| Water table | m | Reported only — drainage details must be designed separately. |
| Base width B | m | Trial footing width for the restoring-moment calculation. |
| Stem t | mm | Reported only. |
| Base friction μ | — | Sliding coefficient between base and soil. Typically 0.5. |
Results: Active coefficient Ka, Passive Kp, Thrust Pa, Overturning and Restoring moments, Factor of safety against overturning and sliding, overall PASS/FAIL. Both FS values must be ≥ 1.5.
10. Electrical tools — field-by-field reference
Electrical 10.1 Ohm’s Law
Enter any two of V, I, R or P — the tool solves for the rest, plus apparent power, reactive power and optional energy cost.
| Field | Unit | What to enter |
|---|---|---|
| System | — | Single-phase/DC, or three-phase. For three-phase, the voltage is line-to-line and √3 is applied. |
| V | V | Voltage. Fill any two of V, I, R, P. |
| I | A | Current. |
| R | Ω | Resistance. |
| P | W | Real power. |
| PF | 0–1 | Power factor. Use 1 for DC or resistive-only loads. |
| Hours/day | h | Used to estimate monthly kWh. Optional. |
| Tariff / kWh | — | Your local price per unit. Optional; fills in the cost row. |
Electrical 10.2 Motor
Full-load current, breaker, minimum cable size and starting current.
| Field | Unit | What to enter |
|---|---|---|
| System | — | Three-phase or single-phase. |
| Power | kW | Motor shaft power (nameplate). |
| Voltage | V | Line-to-line for three-phase, phase for single-phase. |
| Efficiency | % | Nameplate efficiency. Typical IE3 motor ≈ 90%. |
| PF | — | Nameplate power factor. Typically 0.85–0.90. |
| Starting | — | Direct-on-line (~6×), soft starter (~3×), or star-delta (~2×). Used only to estimate starting current. |
Results: Input power, Full-load current, Apparent power, Suggested breaker (next size ≥ 1.25 × FLC), Cable size from the ampacity table, Cable ampacity, Starting current.
Electrical 10.3 PF Fix
Capacitor size required to improve power factor, plus expected current reduction.
| Field | Unit | What to enter |
|---|---|---|
| System | — | Three-phase or single-phase. |
| Load | kW | Active power of the load. |
| Existing PF | — | Measured power factor before correction (e.g. 0.75). |
| Target PF | — | Desired power factor (e.g. 0.95 — many utilities require this minimum). |
| Voltage | V | Line voltage. |
Results: Reactive power before and after, Required capacitor kVAR, next standard 5-kVAR-step bank, current before and after, % reduction in line current.
Electrical 10.4 Cable Drop
Voltage drop, power loss and minimum cross-sectional area for a given cable run.
| Field | Unit | What to enter |
|---|---|---|
| System | — | Single-phase/DC (drop factor 2) or three-phase (drop factor √3). |
| Conductor | — | Copper (ρ = 0.0175 Ω·mm²/m) or Aluminium (ρ = 0.0282). |
| Supply V | V | Nominal system voltage. |
| Current A | A | Design current. |
| Length | m | One-way route length. |
| Area | mm² | Trial cable cross-sectional area. |
| Allowed drop | % | Regulatory limit. Typical 3% (final circuits) or 5% (combined). |
Results: Voltage drop in volts and percent, Cable resistance in mΩ, Power loss in W, Minimum area required to meet the allowed drop, PASS/FAIL.
Electrical 10.5 Transformer
kVA, primary/secondary currents, next standard size.
| Field | Unit | What to enter |
|---|---|---|
| Primary V | V | HV winding voltage. |
| Secondary V | V | LV winding voltage. |
| Load kVA | kVA | Connected load in kVA. |
| Demand factor | — | Ratio of maximum demand to connected load (0–1). |
| PF | — | Power factor of the load. |
| Growth | % | Future capacity allowance (e.g. 20%). |
| %Z | % | Impedance voltage from the transformer nameplate. |
Electrical 10.6 Short-Circuit
Isc at the transformer secondary and at the end of a cable run — simplified IEC 60909.
| Field | Unit | What to enter |
|---|---|---|
| Transformer kVA | kVA | Transformer rating. |
| %Z | % | Impedance voltage. |
| Secondary V | V | LV voltage. |
| Cable length | m | One-way length of the feeder. |
| Cable area | mm² | Cross-section of the feeder. |
| Conductor | — | Copper or aluminium resistivity. |
| Fault time | s | Clearing time used to compute the thermal-equivalent current. |
Results: Transformer full-load current, Isc at terminals, cable resistance, Isc at cable end, thermal Ith, minimum breaker Icu.
Electrical 10.7 Cable Tray
Checks the aggregate cable cross-section against the tray’s permitted fill.
| Field | Unit | What to enter |
|---|---|---|
| Tray width / height | mm | Internal dimensions of the tray. |
| Use | — | Power (40%), Control (50%), Data (60%). Sets the max fill percentage. |
| Cable dia 1–3, Count 1–3 | mm, — | Up to three cable types with their diameters and quantities. Leave 0 to skip a row. |
Results: Tray area, Cable total area, Fill %, Max allowed, Remaining capacity, PASS/FAIL.
11. Mechanical tools — field-by-field reference
Mechanical 11.1 Stress / Strain
Axial stress and elongation, strain, plus torsion on a solid shaft. Fill whichever groups apply.
| Field | Unit | What to enter |
|---|---|---|
| Force F | N | Axial force. |
| Area A | mm² | Loaded cross-section. |
| Length L₀ | mm | Original length. |
| Elongation ΔL | mm | Measured or assumed stretch. |
| E | GPa | Young’s modulus (steel 200, aluminium 69). |
| Torque T | N·m | Applied torque for torsion. |
| Dia d | mm | Shaft diameter. |
| RPM | — | Rotational speed, used to compute power. |
| Shaft length | mm | Length over which the twist accumulates. |
| G | GPa | Shear modulus (steel 80, aluminium 26). |
Results: Axial stress σ, Elongation, Strain, Stress from strain, Polar J, Shear τ, Twist angle, Angular velocity ω, Power in kW and hp.
Mechanical 11.2 Shaft
Combined bending and torsion — von Mises equivalent stress and minimum required diameter.
| Field | Unit | What to enter |
|---|---|---|
| Torque T | N·m | Steady torque transmitted. |
| Moment M | N·m | Bending moment at the critical section. |
| Dia d | mm | Trial shaft diameter. |
| Sy | MPa | Yield strength (355 MPa for S355, 250 for mild steel). |
| SF | — | Safety factor applied to Sy. |
Results: Z, Bending σ, Torsion τ, Von Mises, Allowable stress, Utilization %, Minimum required diameter, PASS/FAIL.
Mechanical 11.3 Fatigue
Basquin-type fatigue life from a stress amplitude.
| Field | Unit | What to enter |
|---|---|---|
| σa | MPa | Alternating stress amplitude. |
| Su | MPa | Ultimate tensile strength. |
| N₀ | cycles | Reference life (typically 1000). |
| Basquin m | — | Exponent (0.1 for steel). |
| Se | MPa | Endurance limit. Below this, life is infinite. |
| Target life | cycles | Required number of cycles for the design. |
Mechanical 11.4 Gears
Simple spur gear pair — ratio, output speed, output torque, centre distance.
| Field | Unit | What to enter |
|---|---|---|
| N₁ / N₂ | teeth | Tooth counts of driver and driven gears. |
| Input RPM | RPM | Driver speed. |
| Input torque | N·m | Torque at the driver. |
| Efficiency | % | Overall mesh efficiency (typically 95–98%). |
| Module | mm | Gear module. Used to compute pitch diameters. |
Mechanical 11.5 Bearing
Basic rating life L10 and required dynamic capacity C.
| Field | Unit | What to enter |
|---|---|---|
| C | kN | Dynamic capacity from the bearing catalogue. |
| P | kN | Equivalent dynamic load. |
| RPM | RPM | Operating speed. |
| Type | — | Ball (exponent 3) or Roller (exponent 3.33). |
| Required life | h | Design target in hours (20,000 h typical for industrial). |
Mechanical 11.6 Belt
Flat/timing belt drive — belt length, tensions and wrap angle.
| Field | Unit | What to enter |
|---|---|---|
| D₁ / D₂ | mm | Pulley pitch diameters. |
| C | mm | Centre distance. |
| RPM | RPM | Driver speed. |
| Power | kW | Transmitted power. |
| μ | — | Friction coefficient between belt and pulley (0.3 typical). |
Results: Ratio, Output RPM, Belt speed, Belt length, Wrap angle (warning below 143°), Tight-side tension T₁, Slack-side T₂, Initial tension, Driver torque.
Mechanical 11.7 Spring
Helical compression spring — rate, stress, deflection, solid height.
| Field | Unit | What to enter |
|---|---|---|
| Wire dia d | mm | Diameter of the spring wire. |
| Mean coil D | mm | Coil centre-to-centre diameter (outside − wire). |
| Active coils | — | Number of active coils. |
| G | GPa | Shear modulus. Steel 79 GPa. |
| F | N | Applied axial force. |
| Ends | — | Plain, Plain & ground, or Squared & ground. Affects the total-coil count. |
Results: Spring index C (warned if <4 or >12), Rate k, Deflection, Shear stress τ, Total coils, Solid height, Free length.
12. Fluid tools — field-by-field reference
Fluid 12.1 Pipe Flow
Reynolds number, friction factor, pressure drop and pump power for a circular pipe.
| Field | Unit | What to enter |
|---|---|---|
| ρ | kg/m³ | Fluid density. Water 1000; air 1.2. |
| μ | Pa·s | Dynamic viscosity. Water 0.001; air 1.8×10⁻⁵. |
| v | m/s | Mean flow velocity. |
| ID | mm | Internal diameter of the pipe. |
| Length | m | Straight pipe length (fittings handled separately). |
| Roughness | mm | Absolute roughness. Steel 0.045; PVC 0.0015; concrete 1.0. |
| Pump η | % | Overall pump efficiency for the power calculation. |
Results: Re, Regime (Laminar / Transitional / Turbulent), Volumetric flow Q, Mass flow, Darcy friction factor f, Pressure drop ΔP, Head loss, Hydraulic power, Pump power.
Fluid 12.2 Orifice
Orifice plate flow rate from a measured differential pressure (ISO 5167 form).
| Field | Unit | What to enter |
|---|---|---|
| Pipe D | mm | Upstream internal diameter. |
| Orifice d | mm | Orifice bore. Must be smaller than D. |
| ΔP | kPa | Measured pressure difference across the plate. |
| ρ | kg/m³ | Fluid density. |
| μ | Pa·s | Fluid viscosity. |
| Cd | — | Discharge coefficient. 0.61 for a sharp-edged orifice. |
Results: β ratio (warned outside 0.2–0.75), Orifice area, Volumetric flow Q, Mass flow, Upstream velocity, Reynolds number.
13. Thermal tools — field-by-field reference
Thermal 13.1 Heat Transfer
One of three modes: conduction, convection or radiation. Pick the mode first.
| Field | Unit | What to enter |
|---|---|---|
| Mode | — | Conduction (needs k and thickness), Convection (needs h), Radiation (needs emissivity). |
| k | W/m·K | Thermal conductivity (steel 50, insulation 0.04, water 0.6). |
| Area | m² | Heat-transfer area. |
| Thickness | m | Conduction path length. |
| T₁ / T₂ | °C | Hot and cold side temperatures. |
| h | W/m²K | Convective coefficient. Air natural 5–25; forced 25–250; water 500–10,000. |
| Emissivity | 0–1 | 0.9 for painted surfaces, 0.05 for polished aluminium. |
Results: Heat rate Q, ΔT, Thermal resistance, Heat flux, Energy per day.
Thermal 13.2 Exchanger
LMTD, required area, effectiveness and NTU for counter-flow or parallel-flow.
| Field | Unit | What to enter |
|---|---|---|
| Arrangement | — | Counter-flow (more efficient) or Parallel-flow. |
| Hot in / out | °C | Hot fluid inlet and outlet temperatures. |
| Cold in / out | °C | Cold fluid inlet and outlet temperatures. |
| Hot flow | kg/s | Hot fluid mass flow rate. |
| Hot cp | kJ/kg·K | Hot fluid specific heat. Water 4.18. |
| Cold cp | kJ/kg·K | Cold fluid specific heat. |
| U | W/m²K | Overall heat-transfer coefficient (water-water 800–1500). |
Results: Heat duty, LMTD, Required area, Cold flow rate, Effectiveness %, NTU.
Thermal 13.3 Wall Layers
Up to three material layers plus inner and outer film coefficients — the classic U-value calculation.
| Field | Unit | What to enter |
|---|---|---|
| Area | m² | Wall area. |
| T inside / T outside | °C | Inside and outside design temperatures. |
| h inside / h outside | W/m²K | Inside and outside surface film coefficients (8 and 25 for typical walls). |
| L1 t / L1 k | mm, W/m·K | Layer 1 thickness and conductivity. |
| L2 t / L2 k | mm, W/m·K | Layer 2 — same. |
| L3 t / L3 k | mm, W/m·K | Layer 3 — same. Leave blank if unused. |
Results: Total thermal resistance R, U-value, Heat flux, Heat rate, Energy per day, and the temperature at each interface.
Thermal 13.4 Pipe Loss
Heat loss per metre from an insulated pipe, compared with the same pipe uninsulated.
| Field | Unit | What to enter |
|---|---|---|
| Pipe OD | mm | Outside diameter of the bare pipe. |
| Insulation t | mm | Insulation thickness. |
| Insulation k | W/m·K | Insulation conductivity (mineral wool 0.04; foam 0.025). |
| Pipe surface | °C | Operating surface temperature. |
| Ambient | °C | Surrounding air temperature. |
| h outer | W/m²K | External convective coefficient (10 for indoor still air). |
| Pipe length | m | Total pipe run. |
Results: Heat loss per metre, Total heat loss, Bare-pipe heat loss per metre, % saved by insulation, Outer surface temperature, Annual energy saved.
14. HVAC tool — field-by-field reference
HVAC 14.1 Cooling Load
Quick sizing of a room cooling load and recommended AC capacity.
| Field | Unit | What to enter |
|---|---|---|
| Length / Width / Height | m | Room dimensions. |
| Wall U | W/m²K | Overall U-value of the fabric (0.5 for a moderately insulated wall). |
| ΔT | °C | Design indoor-outdoor temperature difference (10 typical). |
| Occupants | — | Number of people; 120 W/person sensible + latent. |
| Equipment | W | Heat gain from computers, machinery, etc. |
| Lighting | W/m² | Lighting power density (10 typical). |
| Solar | W | Solar gain through glazing and roof. |
Results: Floor area, Wall+roof area, and a breakdown of fabric, occupant, lighting, equipment and solar gains — plus the total load in W, kW and refrigeration tons, and the recommended AC capacity with a 15% safety margin.
15. Other tools — field-by-field reference
Other 15.1 Vessel
Thin-wall pressure vessel — hoop stress, longitudinal stress, required thickness and MAWP.
| Field | Unit | What to enter |
|---|---|---|
| Shape | — | Cylinder or Sphere. |
| P | MPa | Internal design pressure. |
| ID | mm | Internal diameter. |
| Wall t | mm | Trial wall thickness. |
| S | MPa | Allowable stress of the material. |
| E | 0–1 | Weld joint efficiency (0.85 for typical spot-radiographed joints). |
| CA | mm | Corrosion allowance. |
Other 15.2 Bolt
Bolted joint check — capacity, preload, tightening torque, interaction.
| Field | Unit | What to enter |
|---|---|---|
| Size | — | M6 through M30. The value inside the dropdown is diameter | tensile area. |
| Class | — | 4.6, 8.8, 10.9 or 12.9. The value is proof | ultimate stress. |
| N bolts | — | Number of bolts sharing the load. |
| Tension | kN | Total tensile load on the group. |
| Shear | kN | Total shear load on the group. |
| K | — | Torque coefficient (0.2 for dry, 0.15 for lubricated). |
Other 15.3 Weld
Fillet weld shear capacity and required length.
| Field | Unit | What to enter |
|---|---|---|
| Leg a | mm | Fillet weld leg length. |
| Length per weld | mm | Length of a single weld run. |
| N welds | — | Number of parallel weld runs. |
| Electrode | — | E60 (Fexx = 414 MPa) or E70 (483 MPa). |
| Load | kN | Applied shear force. |
Results: Throat thickness (0.707 a), Total weld length, Shear stress τ, Allowable stress, Capacity, Required length, Utilization %, PASS/FAIL.
Other 15.4 Column
Euler / Johnson column buckling — critical load and utilization.
| Field | Unit | What to enter |
|---|---|---|
| Material | — | E (GPa) and yield strength preset. |
| Ends | — | Effective-length factor K: 1.0 pinned, 2.0 fixed-free, 0.7 fixed-pinned, 0.5 fixed-fixed. |
| I | cm⁴ | Second moment of area about the weak axis. |
| A | cm² | Cross-sectional area. |
| L | m | Actual column length. |
| P | kN | Applied axial load. |
| SF | — | Safety factor applied to the critical load. |
Results: Radius of gyration r, Effective length KL, Slenderness KL/r, Transition slenderness Cc, Mode (Euler vs Johnson), Critical stress, Critical load, Allowable load, Utilization %, PASS/FAIL. A KL/r > 200 warning flags a very slender column.
Other 15.5 Truss
First-pass member forces in a planar truss — chord, diagonal, and utilization.
| Field | Unit | What to enter |
|---|---|---|
| Type | — | Pratt, Howe or Warren (informational). |
| Span | m | Overall truss span. |
| Total load | kN | Total applied load over the span. |
| Panels | — | Number of equal panels (4, 6, 8, 10). |
| Area | mm² | Member cross-sectional area. |
| fy | MPa | Member yield strength. |
| SF | — | Safety factor. |
16. Unit converter
Converts between any two units in twelve categories: Length, Area, Volume, Mass, Force, Pressure, Energy, Power, Speed, Torque, Flow and Temperature.
- Select a Category — e.g. Pressure.
- Type a Value — e.g. 1.
- Pick the From unit — e.g. Bar.
- Pick the To unit — e.g. PSI.
- Result appears immediately. The full list of equivalent values in every other unit in that category is shown below the two highlighted rows.
The Swap units button inverts From and To in one click. Temperature is handled as an affine conversion (not just a scale factor), so Celsius → Fahrenheit and Celsius → Kelvin both work correctly.
17. Where to apply these calculations
Structural engineering
- Preliminary sizing of steel floor beams, roof purlins, and transfer beams.
- Reinforced concrete beam and one-way slab design to Eurocode 2 / ACI 318.
- Pad footing sizing from column load and allowable soil bearing pressure.
- Retaining wall stability checks — overturning and sliding factors of safety.
- Load combination envelopes per ASCE 7 LRFD and Eurocode ULS.
- Column buckling capacity using Euler and Johnson curves.
- Bolted joint interaction using von Mises-style combined tension and shear.
Electrical engineering
- Motor full-load current, breaker sizing, and cable selection.
- Cable voltage drop for feeders and long runs; minimum area to meet a 3% drop limit.
- Power factor correction capacitor sizing in kVAr.
- Transformer kVA sizing with future growth allowance and standard IEC sizes.
- Short-circuit current at the transformer secondary and at the end of a feeder.
- Cable tray fill percentage for power, control, and data cables.
Mechanical engineering
- Shaft diameter sizing under combined bending and torsion.
- Fatigue life estimation using the Basquin equation.
- Gear ratio, output torque, and centre distance from module and tooth counts.
- Bearing L10 life and required dynamic capacity C.
- Belt length, tensions, and wrap angle.
- Compression spring rate, stress, and solid height.
Fluid, thermal and HVAC engineering
- Pipe flow Reynolds number, friction factor, and pressure drop.
- Orifice plate flow rate from differential pressure per ISO 5167.
- Heat exchanger LMTD, area, and effectiveness-NTU.
- Multi-layer wall heat loss and temperature profile.
- Insulated pipe heat loss versus bare pipe.
- Cooling load for a space from area, occupants, lighting, and solar gain.
18. Common mistakes to avoid
1. Mixing units
Every field shows its unit in parentheses. Do not mix millimetres with metres in the same calculation. If you are unsure, convert to base units (mm, kN, MPa) before entering.
2. Forgetting self-weight
The Beam tool reports beam self-weight separately and does not add it to your applied load. For long spans or heavy sections, add the beam’s own weight to the applied load. The RC Beam and Slab tools do include self-weight.
3. Using service loads in a strength check
The strength checks compare your moment against an allowable stress derived from yield ÷ safety factor. If your code requires LRFD/ULS load combinations, apply those factors first using the Load Combo tool, then enter the factored load into the Beam tool.
4. Ignoring deflection limits
A beam can pass the stress check and still fail the serviceability check. Watch the Span / deflection row. Limits vary — L/360 for floors, L/240 for roofs, L/180 for cantilevers — so confirm against your project specification.
5. Assuming singly reinforced when K exceeds Kbal
The RC Beam tool switches automatically to doubly reinforced when K is above the balanced value and reports the required compression steel. Do not ignore the note in the results panel.
6. Forgetting the demand factor
Transformer sizing uses a demand factor for the connected load. Oversized transformers idle at low efficiency; undersized ones run hot. Use the demand factor field explicitly.
19. Key user pain points and how AlamToolKit solves them
| Pain point | Typical free calculator | AlamToolKit solution |
|---|---|---|
| Numbers without context | Returns a single value with no visual. | SFD, BMD, and deflection charts drawn automatically for beam problems. |
| No design iteration | You re-enter every value from scratch. | Compare A/B: pin the current result, change one input, see the delta instantly. |
| Losing work between sessions | Refresh loses everything. | Named projects and starred tools stored in your browser. |
| Client reporting friction | Screenshot the browser window. | PDF/PNG export with logo, and CSV/BoQ export for Excel. |
| Sharing a calculation | Send a screenshot and re-enter numbers by hand. | One-click share link encodes every input into the URL. |
| Finding the right tool | Bookmark a dozen separate sites. | Search box jumps to any of 35 tools by name. |
| Slow, heavy pages | Ads, trackers, and analytics scripts. | Zero trackers, no external requests, works offline. |
20. Accuracy and scope — please read
Every formula in Engineering Calculator is drawn from standard engineering references: mechanics of materials, AISC steel manual conventions, Eurocode 2 and ACI 318 for reinforced concrete, ASCE 7 and Eurocode for load combinations, IEC 60909 for short-circuit calculations, ISO 5167 for orifice flow, and ASHRAE methods for cooling loads.
That said, no calculator replaces engineering judgement. The toolkit uses standard closed-form solutions and simplified assumptions:
- Beam formulas assume linear-elastic material behaviour, prismatic sections, and no local buckling or lateral-torsional buckling checks.
- RC beam and slab checks cover flexural reinforcement only — not shear reinforcement, crack width, or deflection by integration.
- Electrical calculations use nominal values and simplified IEC 60909 assumptions. Cable impedance and motor starting transients may require more detailed modelling.
- Fluid and thermal tools assume steady state and constant properties.
21. Real-world usage scenarios
On site — verifying a beam before installation
A site engineer receives a UB section that was delivered at a shorter depth than specified. Before refusing delivery, they open Engineering Calculator on a phone, enter the delivered dimensions, and check whether the bending stress and deflection still pass. The Compare A/B table shows the delta against the original design. Decision made in two minutes.
During tender — sizing for a quotation
An electrical contractor needs to quote a motor feeder. They use the Motor tool for full-load current, the Cable Drop tool for voltage drop on the proposed route, and export the results as BoQ CSV to build the pricing sheet.
Design review — producing a calc package
A structural engineer stars the ten tools used on a project, saves them under the project name, and clicks PDF. The resulting PNG includes the logo, the date, and every input and result — ready to attach to a design file or send to a checking engineer.
Teaching — demonstrating the effect of boundary conditions
A lecturer switches a beam from simply supported to cantilever in the Beam tool. The deflection chart changes shape and the maximum value jumps by a factor of 16. Students see the difference instantly.
22. Keyboard shortcuts
| Key | Action |
|---|---|
| Enter (in any input) | Runs the current tool’s calculation. |
| ← / → (on a tab) | Moves to the previous / next tab in the current category and opens it. |
| Tab | Moves between input fields. |
| Ctrl+P | Prints the current calculation in a clean, code-friendly layout. |
23. Troubleshooting
| Symptom | Likely cause and fix |
|---|---|
| Red error message appears under the inputs | A required field is missing or has an invalid value (e.g. thickness bigger than height). Read the message — it tells you exactly which field to fix. |
| Charts don’t appear | You are on a tool other than Beam. Charts are only shown for the Beam tool because it is the one with closed-form shear/moment/deflection equations. |
| Nothing happens on Calculate | Check the browser console for errors (F12 → Console). Usually caused by a stray character when pasting the code — reload the page. |
| Favourites / projects disappear | You cleared your browser’s site data, or you’re in private/incognito mode. Favourites, projects and dark mode are stored per browser, not on a server. |
| PDF downloads as PNG | That is intended. The file is a high-resolution raster image (PNG) that prints cleanly and pastes into Word, PowerPoint and email without font issues. |
| Unit converter shows no units | Choose a Category first; the From and To dropdowns populate from that choice. |
| Numbers look wrong on a phone | Your device keyboard may interpret a comma as a decimal separator. Use a period (.) or switch the phone’s locale to English. |
24. Frequently asked questions
Is Engineering Calculator free to use?
Yes. All 35 calculators are free. There is no login, no subscription, and no watermark on exported reports.
Does it work offline?
Yes. Once the page has loaded, it will keep working with no internet connection. Everything runs in your browser.
Where are my inputs and projects stored?
In your browser’s localStorage, on your device only. Nothing is uploaded to a server. Clearing browser data will remove saved projects.
What codes and standards are used?
ASCE 7 and Eurocode load combinations, Eurocode 2 and ACI 318 conventions for RC flexure, AISC-style allowable stress for steel, IEC 60909 for short-circuit, ISO 5167 for orifice flow, and ASHRAE methods for cooling loads. See the Accuracy section above.
Can I use it for final design?
Use it for preliminary sizing, routine checks, and iteration. Critical designs must be verified against the applicable code and reviewed by a qualified engineer.
Why does the Beam tool warn that self-weight is not added?
Because self-weight depends on the section you chose and on how you have factored the load. For accuracy, add the reported self-weight to your applied load before entering it.
Can I share a calculation with a colleague?
Yes. Click Copy share link in any tool. Every input is encoded into the URL. Anyone opening the link sees the same values.
How do I export results to Excel?
Star the tools you want, then click 📊 BoQ CSV. Every result row from starred tools is exported as a CSV file you can open in Excel.
Why did my result change when I switched support type?
Because the moment, shear, and deflection formulas depend on the boundary condition. A cantilever with an end point load has a moment of P·L and deflection P·L³/(3EI), versus P·L/4 and P·L³/(48EI) for a simply supported beam. The charts show the difference visually.
Can I use it on my phone?
Yes. The layout is responsive and the canvas charts scale to fit small screens. Numbers and results are readable on phones from 360 px wide upward.
What happens if I enter an invalid value?
A red error message appears telling you which field to fix. No calculation runs until the input is corrected. See the input validation list in Section 3 above.
Do you collect any analytics?
No. The calculator makes no external requests. Your inputs stay on your device.
25. Disclaimer
Results are for preliminary estimation only. Every formula used in this calculator is a simplification of the corresponding design code. Before construction, fabrication or energisation:
- Verify all inputs against the applicable code (Eurocode, ACI, ASCE, BS, IEC, ISO, ASHRAE, etc.).
- Check every critical design — especially strength, stability, deflection and fatigue-sensitive members — independently.
- Have the final design reviewed and signed off by a qualified engineer licensed in your jurisdiction.
The authors and AlamToolKit.com accept no liability for any loss, damage or injury arising from the use of these results.
Engineering Calculator — user guide v1.0
© AlamToolKit.com
