NEC Electrician Calc: VoltKit

NEC-based field calculators: voltage drop, wire size, ampacity, conduit & box fill, Ohm's law, bending. Fully offline. No subscription, no ads. One-time Pro unlock.

The electrician's calculator that works where you do - in the basement, in the panel, in the dead zone.

VoltKit is a fast, no-nonsense field calculator for electricians, apprentices, estimators, and inspectors. Six pro calculators, grounded in the National Electrical Code (NFPA 70), all running 100% on your phone. No account. No login. No internet. Just answers.

FULLY OFFLINE - ALWAYS Crawlspaces, mechanical rooms, new construction with no service yet - VoltKit needs zero signal. Every table, every formula, every result is computed on-device. Drop into a concrete basement and it works exactly the same as it does on the roof. Your data never leaves your phone because there's nothing to send.

NEC-GROUNDED, NOT GUESSED The numbers come straight from the code book - ampacity from Table 310.16, the 240.4(D) small-conductor rules, conduit and conductor areas from Chapter 9, box-fill volumes from 314.16(B), and EMT take-up for stub-ups. Real values, not approximations. (Estimation aid only - always verify against the current NEC and your local AHJ.)

SIX PRO CALCULATORS

• Voltage Drop: single- or three-phase, copper or aluminum, any AWG/kcmil. Volts dropped, % drop, voltage at the load, a pass/fail on the 3% / 5% recommendations, and the smallest wire size that keeps you in spec.
• Wire Size & Ampacity: the 60/75/90C ampacity for any conductor, the 240.4(D) overcurrent cap, and the minimum wire size for a load.
• Conduit Fill: EMT, RMC, IMC, PVC 40/80, ENT; add your conductors and get the minimum trade size plus fill % at every size against the 53% / 31% / 40% limits.
• Box Fill: conductors, clamps, device yokes, support fittings and grounds; required cubic inches and a fit check against your box's marked volume.
• Ohm's Law: enter any two of volts, amps, ohms, watts and solve the other two.
• Conduit Bending: offsets (distance between bends + shrink), 90-degree stub-ups (first-bend mark from take-up), and three-point saddles.

SAVE THE JOB Tag any calculation as a saved job - load, length, wire, result - so the panel schedule, the rough-in, and the inspection note are one tap away.

ONE-TIME PRO. NO SUBSCRIPTION. EVER. VoltKit is free to try. Unlock VoltKit Pro once for $9.99 and keep it: unlimited saved jobs, plus PDF and share export to send a clean one-page result to the GC, the office, or the file. One payment, handled by Apple.

WHO IT'S FOR Journeymen and apprentices, residential and commercial electricians, estimators and project managers, electrical inspectors, maintenance and facilities techs.

VoltKit is an estimation tool and is not a substitute for a licensed electrician's judgment. Always verify results against the current edition of the NEC (NFPA 70) and your local authority having jurisdiction (AHJ).