Conduit Fill API
NEC conduit-fill and box-fill maths as an API, computed locally and deterministically — the electrical-code calculations an electrician or estimator does on every run. The conduit-fill endpoint takes a set of conductors (as size:count pairs, e.g. 12:3,10:2) and a conduit trade size and returns the conductor cross-sectional area, the conduit's internal area, the fill percentage and whether it stays within the NEC Chapter 9 limit — 53 % for a single conductor, 31 % for two, 40 % for three or more — so nine #12 THHN fill a half-inch EMT to 39 % (legal) but ten do not. The box-fill endpoint applies NEC 314.16(B): each conductor adds its free-space allowance (2.00 in³ for #14, 2.25 for #12, and so on), a device yoke counts as two, internal cable clamps as one, and all equipment grounds together as one — all at the largest conductor's volume — to give the minimum junction-box size, checked against a box volume if you give one. Uses the THHN/THWN and EMT areas from NEC Chapter 9. Everything is computed locally and deterministically, so it is instant and private. Ideal for electrical-contractor, estimating, inspection and electrician app developers, conduit and box-sizing tools, and apprentice training. Pure local computation — no key, no third-party service, instant. Imperial: square inches and cubic inches. Live, nothing stored. 2 compute endpoints. Always verify against the adopted code edition — this is an estimating aid, not an inspection.
api.oanor.com/conduit-api
