Electrician Calculator Toolkit

Eight electrician calculators built for the job site: fast, accurate, and fully offline. Every result shows the code table it came from, so you can check it against the book or explain it to the inspector.

VOLTAGE DROP
Single-phase, three-phase or DC. Copper or aluminum, #14 AWG to 750 kcmil, feet or meters, parallel sets. See the drop in volts and percent, the voltage at the load, and the smallest conductor that stays under 3%.

WIRE SIZE (AMPACITY)
Enter the load, mark it continuous, pick 60/75/90°C terminations and the material. The app applies the 125% rule, the ambient-temperature correction and the adjustment for more than three current-carrying conductors, respects the small-conductor limits, and shows the adjusted ampacity of every size around the answer.

CONDUIT FILL
Add any mix of conductor sizes and insulation types (THHN/THWN, XHHW, THW) and get the minimum trade size for EMT, PVC Schedule 40 and 80, RMC and IMC side by side. Or flip it around: how many #12 THHN fit in a 3/4" EMT?

BOX FILL
Count the conductors entering the box, add clamps, devices, support fittings and equipment grounds, and compare the required volume against the box you have.

LOAD & BREAKER
From watts, voltage, phase and power factor to load current, design current, the next standard breaker rating and the minimum 75°C conductor.

OHM'S LAW
Enter any two of voltage, current, resistance and power. The other two appear instantly.

RESISTOR COLOR CODE
Four- and five-band decoding with tolerance.

CODE TABLES
Ampacity tables for copper and aluminum, standard breaker ratings, ambient-temperature and conductor-count derating factors, box fill volumes and common box sizes, and wire color conventions for US and IEC systems.

MADE FOR THE FIELD
• Works with no signal: nothing is downloaded, nothing is uploaded
• No account, no subscription, no ads, no analytics
• Dark interface that stays readable in a panel or a crawl space
• Available in 19 languages

Reference values follow the tables of the 2023 edition of the US National Electrical Code (NFPA 70). This app is a calculation aid, not a substitute for the code, engineering judgement or the authority having jurisdiction. NEC and National Electrical Code are registered trademarks of the National Fire Protection Association, which does not sponsor or endorse this app.