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.
Free to download. AmpRule Pro is a $14.99 one-time purchase — no subscription.
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.
What it looks like
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.
NEC calculators
The same engines that ship in the app, running right here. Every result shows the arithmetic and the article behind it. No sign-up, no ads, and nothing you type leaves your browser.
NEC guides
Worked explanations of the calculations that come up on the job, each citing the article it comes from. Useful on their own — you do not need the app to get the answer.
Common questions
- Is there a subscription?
- No. AmpRule Pro is a single $14.99 purchase and it stays unlocked, including future NEC editions. There is no subscription tier and there never will be one.
- Does it work without a signal?
- Yes. Everything runs on the device — the tables, the calculators, the search. There is no account, no login, and no network request, so it works in a basement, a crawl space, or a mechanical room.
- Which NEC editions does it cover?
- The 2017, 2020, 2023 and 2026 editions all ship with the app. You switch between them from any screen where the edition changes the answer, and the tables, results and cited article numbers all follow your selection.
- Will an update take features away?
- No. Removing a feature people rely on is the fastest way to lose their trust, and it is the single most common complaint in this category. Updates add; they do not subtract.
AmpRule is not affiliated with or endorsed by NFPA. NEC and National Electrical Code are trademarks of the National Fire Protection Association.