NEC Box Fill Calc

About

Catch an overfilled box before rough-in inspection fails. NEC Box Fill Calc helps electricians run a fast NEC 314.16(B) field check on site, see exactly where the volume went, and spot the smallest listed box that fits before rework starts. Free field check: - Add conductors by gauge from 18 AWG through 6 AWG - Count grounding conductors, internal clamps, support fittings, and devices correctly - See total fill, pass/fail status, line-by-line breakdown, and the smallest listed standard box that fits - Switch between 20 standard box sizes or enter a custom marked volume - Work fully offline with no account, ads, or subscription Unlock Inspection Cards once to: - Save inspection cards on device - Pin important cards for repeat rough-in work - Reload a saved card back into the free check workflow - Share or export a plain-text inspection summary - Restore lifetime access on another device Built for electricians, apprentices, and foremen who want to avoid repulls, box swaps, and inspection-day surprises. Important: - Always verify the enclosure's marked volume and local requirements on site. - This app is a practical field aid, not a substitute for code judgment or inspection approval.