Worldwide cable sizing estimator
Cable Sizing Calculator
Size cables from load and route length - current capacity and voltage drop together, copper or aluminium, any voltage system. Multiple circuits in one job, with a cable-to-order total by size.
Worldwide cable sizing estimator
Size cables from load and route length - current capacity and voltage drop together, copper or aluminium, any voltage system. Multiple circuits in one job, with a cable-to-order total by size.
Enter a load directly in amps, or as power and power factor - the recommended cable satisfies both derated current capacity and your job's voltage-drop limit, whichever needs the bigger cable.
230V single-phase, 400V/415V three-phase, 120V/240V US split-phase, 480V, or a custom voltage - copper or aluminium conductors, metric or imperial units.
Add every circuit in a job and see the total cable length to order, grouped by size - no separate tally per circuit.
Correction factors for ambient temperature, how many circuits are grouped together, and installation method (clipped, enclosed, buried, tray) all derate the cable before a size is chosen.
Name each circuit for a job that reads back clearly, then copy a plain-text summary or export the whole job as a standalone HTML file to keep, print or send on.
A layout that spreads across a wide window, a light/dark toggle that remembers your choice, and a rotating set of realistic sample jobs to load and explore.
Trimble's electrical design software (formerly Amtech ProDesign/Cable Calc) is the well-known professional package UK electrical consultants use for BS 7671 cable design across a whole installation - here's how a focused, one-off contractor tool compares.
| Feature | Cable Sizing Calculator | Trimble Cable Calc |
|---|---|---|
| Pricing model | One-off purchase after a free trial | Enterprise licence, custom quote (no public pricing) |
| Works fully offline | ✓ | ~ |
| Instant standalone circuit check, no project setup | ✓ | ✕ |
| Multiple circuits rolled into one cable-to-order total | ✓ | ✓ |
| Full electrical schematic design & compliance certification | ✕ | ✓ |
| Manufacturer cable database integration | ✕ | ✓ |
| Built for a quick contractor sense-check rather than a design engineer | ✓ | ✕ |
| Requires specialist training to get full value | ✕ | ✓ |
Comparison based on Trimble/Amtech's publicly listed product information as of August 2026 (trimble.com, mep.trimble.com, amtech-power.co.uk) - features and availability change over time, so check trimble.com for current details. Trimble and Cable Calc are trademarks of their respective owner; this comparison is for informational purposes and isn't sponsored by or affiliated with Trimble.
Two very different circuits in one job - a kitchen cooker sized from its power in kW, and a garage supply buried in the ground sized from its current - with cable to order totalled at the end.
The garage run needs a bigger cable than the cooker despite a similar current because burial derates the conductor and the route is longer. Push the garage route out to 90 m and the recommendation steps up to 16 mm², now sized by voltage drop rather than current capacity - the app tells you which constraint won. Open the browser edition to try it with your own figures.
No - use it straight from your browser, on a phone, tablet or PC, with no sign-up. It works offline once it has loaded, and you can add it to your home screen or desktop like an app. There is also a Windows desktop version in the Microsoft Store if you prefer an installed app.
One account covers all of it: Cable Sizing Calculator, Vector, Forma and every other Keystone app share the same sign-in.
No - it's a quick sizing sense-check from generic, rounded reference values, not a certified design. Always verify against your local wiring regulations (BS 7671, NEC, AS/NZS 3000 or equivalent) and get work designed, inspected and certified by a qualified electrician as required in your jurisdiction.
Yes - pick a voltage system (230V single-phase, 400V three-phase, 120V/240V US split-phase, 415V, 480V, or a custom voltage), copper or aluminium conductor, and metric or imperial units.