NEC Box Fill Calc

Box Fill Calc helps electricians verify NEC 314.16(B) compliance for every junction box — in seconds, right on the job site. Count Each Wire: - Add conductors by gauge (18 AWG through 6 AWG) with exact counts - Grounding conductors, internal clamps, support fittings, and devices all count correctly per NEC rules - Every conductor has its proper NEC Table 314.16(B) volume allowance Know Instantly: - Total fill in cubic inches with a clear pass/fail result - Line-by-line breakdown so you can see exactly what's using your box volume - How much room is left — or how much you're over Switch Box Sizes Fast: - 18 standard box sizes from NEC Table 314.16(A): round, square, device, and masonry - Custom box volume for specialty enclosures - See the marked volume for every standard box size Why electricians choose Box Fill Calc: - One-tap recalculate when you change a count or toggle a fitting - Works offline — no cell service needed on the job site - One-time purchase, no ads, no account, no subscription - Clean, high-contrast interface for bright sunlight and dim mechanical rooms Made for journeyman electricians, apprentices learning code, inspectors double-checking fill, and anyone who wires junction boxes and wants to pass inspection the first time.