AmpRule
Electrician Calc & NEC Ref
A National Electrical Code reference handbook and calculator set for electricians in the United States. Every answer comes with the article number it is based on, and the whole thing works offline.
Every result cites the Code
Each calculation shows the NEC article number it comes from, so you can check the reasoning and point to it on the job.
Four Code editions built in
NEC 2017, 2020, 2023, and 2026 ship with the app. Switch editions to match the code cycle your jurisdiction is on.
Fully offline
Everything runs on the device. It works in a basement, in a crawl space, or anywhere else without a signal.
No account, no ads
No sign-up, no login, no advertising, and no data collection. Open the app and use it.
Calculators
Wire sizing
One pass gives you the conductor, OCPD, equipment grounding conductor, conduit size, maximum length, and voltage drop.
Voltage drop
Drop and percentage for a run, with the governing article cited.
Conduit fill
Raceway fill by conductor count, size, and conduit type.
Box fill
Required box volume from conductors, devices, clamps, and fittings.
Motor circuits
Motor branch-circuit sizing from the NEC motor tables.
Conduit bending
Offsets, saddles, and stub-ups with the marks laid out for you.
Ohm's law
Volts, amps, ohms, and watts solved from any two known values.
Free to download. $14.99 once for Pro.
AmpRule is a free download with a single in-app purchase that unlocks Pro. It is a one-time purchase — there is no subscription.
AmpRule is not affiliated with or endorsed by NFPA. NEC and National Electrical Code are trademarks of the National Fire Protection Association.