Electrical Calculator: NEC

Pro electrical calculators with no subscription and no ads. Ohm's law, voltage drop, wire sizing, conduit and box fill, motor and transformer. Pay once.

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.