About HardHatMath

HardHatMath is a free hub of construction and trade math calculators for US professionals — electricians first. No accounts, no paywalls, no lead-capture forms. Type your numbers, get an answer you can check against the code.

Why this site exists

Most trade calculators online bury the answer under ads, skip the code reference, or hide the math entirely. On a job site you need the opposite: a fast page that works on a phone, shows the formula it used, and tells you which code section it came from — so you can look it up yourself instead of taking a website's word for it.

How the calculators are built

Every electrical tool is computed against the NEC 2023 (NFPA 70) and cites the specific section or table it uses — you can read the source yourself via NFPA's free access to the code. Formulas come from public, primary sources only: the code itself, published standards, and standard electrical theory. No vendor charts, no "trust us" numbers.

Before a calculator ships, its math is run through automated tests that cross-check results against the published code tables and against established references. The engine computes in SI units internally and converts only at the edges, so a result never drifts because of sloppy unit math. When a tool needs an assumption (conductor temperature rating, power factor, demand factors), the assumption is stated on the page, not hidden.

What HardHatMath does not do

HardHatMath gives you the math — nothing else. It does not interpret the code, does not provide engineering services, and does not tell you what passes inspection. Jurisdictions adopt different code editions with local amendments, and the authority having jurisdiction (AHJ) always has the final say. Every result here is an estimate to be verified by a licensed professional. See the full disclaimer.

Found a wrong number? Tell us — accuracy is the whole point. Or head to the electrician calculators →