About this app
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.
Latest release
What’s New
Free core box fill checks now stay open. Added the one-time Inspection Cards unlock for saved cards, pin/load workflow, sharing, export, restore, and grandfathering for paid-era users.
Audience growth
Ratings growth
Baseline captured. Growth appears after the crawler observes a changed rating count.
Momentum comes from crawler snapshots for the tracked storefront. “Viral growth signal” means unusually fast recent rating gains; it is an indicator, not download data.
Price tracking
Price intelligence
First snapshot captured. The trend line starts after the next crawler price observation.
- First observed Aug 27, 2026 · 1:25 AM Free
Screenshots
