Electrical Calculator: NEC

Electrical Calculator is a fast, offline toolkit for electricians, students and DIY pros - with no subscription and no ads.

The core calculators are free forever. Unlock Pro once (no subscription, ever) for the full professional set.

FREE
- Ohm's Law: enter any two of volts, amps, ohms, watts
- Energy cost: power, hours and rate to kWh and cost
- Series and parallel resistance

PRO (one-time)
- Voltage drop: wire, load and length to drop, percent and end voltage
- Wire size: smallest AWG for load and voltage drop
- Ampacity: AWG to amps (NEC 310.16, 75C) with breaker limits
- Conduit fill: EMT and THHN to percent fill
- Box fill: conductors and devices to required volume (NEC 314.16)
- Motor FLA: HP and voltage to full-load amps, conductor and breaker
- Three-phase power and current, transformer kVA
- Power factor correction, conduit bending, wire resistance, amps to kW/HP

MORE
- Works fully offline, no account, no tracking
- Light and dark themes, English and Russian
- Paperless tape: save and share your results

Estimates are based on the NEC. Always verify against your local code and the authority having jurisdiction. This app is a tool, not a substitute for a licensed electrician.