Box Fill Pro - Electrician

NEC 2023 box fill calculator for electricians. Calculates conductor, device, and fitting allowances per Article 314.16. Pass/Fail verdict. Offline. One-time purchase.

Box Fill Pro calculates electrical box fill per NEC 2023 Article 314.16 — the code section that determines how many wires, devices, and fittings can legally fit in a junction or device box.

Works offline. No subscription. One-time purchase.

WHAT IT CALCULATES

• Line-voltage conductors by AWG gauge (14, 12, 10, 8, 6)
• Equipment grounding conductors (all EGCs combined = one allowance, per 314.16(B)(5))
• Internal cable clamps (all clamps = one allowance, per 314.16(B)(2))
• Luminaire studs and hickeys
• Strap-mounted devices (switches, receptacles)

VERDICTS BACKED BY CODE Compares your fill total against NEC Table 314.16(A) box capacities. Get an instant PASS or FAIL — and a suggested upgrade if you're overfilled.

BUILT FOR THE FIELD No ads. No cloud. No account required. Designed for electricians who need the answer in seconds, not after a signup flow.

PART OF THE FIELDMETRIC SUITE Also available: Conduit Fill Pro (NEC conduit fill calculations).