Cable Sizing: Wire & Conductor

Size conductors with confidence, based on NEC (NFPA 70) and CEC (CSA C22.1) requirements.
Cable Sizing is a calculator for electricians, designers and engineers who need a correct conductor size and a clear reason for it — not just a number. Enter the load, pick the installation method, and get the required size with the ampacity, voltage drop and termination limits behind it.
What it handles:
- Copper or aluminum, 60/75/90 degree C insulation, with termination-rating limits applied per code
- Free air, raceway/conduit, cable tray, and underground (direct buried or in conduit/duct bank)
- Parallel sets — auto-optimized or user-specified, with separate-raceway handling
- Voltage drop, with an optional enforced limit
- DC circuits, plus single-phase and three-phase AC
- Medium-voltage class conductors (90/105 degree C, single or triplex, shielded/grounded options)
- CEC-specific inputs: cable arrangement, spacing, duct count, duct-bank vs. direct burial, MV outdoor exposure
- Ambient temperature correction and adjustment for other current-carrying conductors in the same raceway
- Continuous-load and 100%-rated equipment handling
- A full calculation trail with the applicable NEC/CEC references, available to review
- Both NEC and CEC modes, for US and Canadian jobs alike
Built for a phone: a short step-by-step flow, and a two-pane layout with inputs and results side by side on a tablet or in split-screen. The result leads with the conductor size and the key figures — ampacity, voltage drop, suggested overcurrent protection — with the full steps available to expand.
Calculations run on your device. An internet connection is used occasionally to confirm your trial or purchase status, not to perform the calculation itself.
Access: every feature is unlocked for a 7-day free trial. After that, the app stays fully functional for up to 5 complete calculations per month at no cost. A one-time in-app purchase removes that monthly limit permanently — no subscription.
Cable Sizing is not affiliated with or endorsed by NFPA or CSA Group. Results are an engineering aid intended to support, not replace, the professional judgement of the engineer or designer of record, and do not account for every local amendment or site condition. Always verify against the adopted code edition for your jurisdiction. No warranty of any kind is expressed or implied.