Electrician · Sources
Sources & References
Every table backing these calculators was cross-checked against at least one independent published source before being encoded. Here's exactly where the numbers came from.
NEC reference tables
Ampacity (Table 310.16), box fill (Table 314.16(A)/(B)), conduit & conductor areas (Chapter 9, Tables 1/4/5/8), and motor full-load current (Table 430.247/248/250/251(A)) were verified from a full NEC reference-table compilation and cross-checked against independent published sources.
We do not host or redistribute the NEC code book itself (it's NFPA-copyrighted) — only the factual numeric values were used to build our own data files, same as every other electrical calculator site.
Table numbers have shifted across NEC editions (310.16 → 310.15(B)(16) in 2014–2020 → back to 310.16 in 2023), but the ampacity/area/volume/FLC values for standard copper & aluminum building wire have stayed the same for decades. Always confirm the article/table number for your state's currently adopted edition.
Voltage drop K constant
K = 12.9 (copper) / 21.2 (aluminum) is the industry-standard approximate DC resistance constant used across the trade and in exam prep, derived from NEC Chapter 9 Table 8 resistance data — not a single NEC-mandated value.
State licensing requirements
Texas, California, and Florida are fully verified against the official state board and exam vendor — see state licensing requirements. New York and Pennsylvania don't have a single statewide electrician exam to verify (licensing is set locally in both), so they weren't built into full pages yet.
Federal & state PDFs
Public-domain federal references (OSHA 29 CFR 1926 Subpart K, via the official Government Publishing Office CFR compilation) and official state board documents that are safe to redistribute are saved here:
- OSHA 29 CFR 1926 Subpart K — Electrical (2025 CFR, PDF)
- TDLR "Electricians at a Glance" (Texas, PDF)
- DBPR Electrical Contractors' Candidate Information Booklet (Florida, PDF)
Copyrighted vendor content (PSI and Pearson VUE candidate bulletins) is linked to its official source instead of being rehosted here.
In progress
Article 220 dwelling-unit load tables (for the upcoming Dwelling Unit Load Calculator) have verified data saved, but the calculator itself isn't built yet. More states are being researched next.
Full machine-readable manifest: sources.json. This manifest and the calculator data files are provided for reference and citation, not for bulk reuse in a competing product — see Terms of Service.