NEC Box Fill Calc

About

NEC Box Fill Calc gives electricians a complete NEC 314.16(B) single-box field check at no charge. When a job spans multiple boxes, the existing Rough-In Schedule keeps labels and corrections together for a shareable handoff. 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 the Rough-In Box Schedule once to: - Name the current project and label each box or room - Collect up to 30 completed box checks on device - See project totals for passing and overfilled boxes - Put every required correction first, including overage, current box, and recommended replacement - Reload any scheduled check into the free calculator - Share or export one complete plain-text schedule - 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.