Wire Sizing Calculator
The Wire Sizing Calculator picks the conductor size (mm²) for a load, applying continuous-load, temperature, and conduit-fill derating plus a voltage-drop check. Example: for a 50 kW 3-phase 400 V feeder, 40 m long, at 35 °C ambient, Conductor size = 30 mm², Design current = 84.9 A, Derated ampacity = 108.1 A (per PEC 2017 | NEC 2020 | IEC 60364-5-52 | IEC 60228).
How it works
Computed from your inputs per PEC 2017 | NEC 2020 | IEC 60364-5-52 | IEC 60228.
Worked example (Electrical & Power)
Inputs: a 50 kW 3-phase 400 V feeder, 40 m long, at 35 °C ambient.
| Result | Value |
|---|---|
| Conductor size | 30 mm² |
| Design current | 84.9 A |
| Derated ampacity | 108.1 A |
Computed live by WorkHive's calculation engine; standard: PEC 2017 | NEC 2020 | IEC 60364-5-52 | IEC 60228.
How to use this calculator
- Enter the figures for the duty you are sizing: the worked example below uses a 50 kW 3-phase 400 V feeder, 40 m long, at 35 °C ambient.
- The calculator returns Conductor size, Design current, Derated ampacity, computed per PEC 2017 | NEC 2020 | IEC 60364.
- Check the worked example to confirm the method matches how you would do it by hand, then run your own numbers in the interactive tool.
FAQ
What is a electrical wire size calculator kW?
The Wire Sizing Calculator is a free online tool that computes picks the conductor size (mm²) for a load, applying continuous-load, temperature, and conduit-fill derating plus a voltage-drop check. It shows the formula and a fully worked example so you can check the method, not just the number.
How is it calculated?
The result is computed from your inputs following PEC 2017 | NEC 2020 | IEC 60364. The worked example on this page shows a real computation with real numbers.
Is the calculator free?
Yes. WorkHive's engineering calculators are free to use, no sign-up needed for the tools. WorkHive is a free, offline-first maintenance platform built for Philippine industrial plants.
Run it on your own numbers
Open the interactive Wire Sizing Calculator in WorkHive: free, no sign-up needed for the calculators.