Electrical Calculators
Field-ready calculators built to NEC tables. Free, fast, and mobile-friendly — made for the tailgate, usable by anyone.
Voltage Drop
Single- and three-phase voltage drop by wire size, with the minimum size that meets the NEC 3% recommendation.
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🧵Conduit Fill
THHN in EMT against Chapter 9 fill limits — mixed conductor sizes supported, with the minimum conduit size for the pull.
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📦Box Fill
Conductor, device, clamp, and ground counting per 314.16 — with the smallest standard box that passes.
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🔥Ampacity & Derating
Table 310.16 with ambient temperature correction and bundling adjustment — copper and aluminum.
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🏠Residential Load Calc
Article 220 standard-method dwelling calculation with the demand math shown and a suggested service size.
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⚙️Motor Calculations
Table FLA, conductor sizing at 125%, and max breaker/fuse per Table 430.52.
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Calculator results are estimates for reference. Verify all values against the current National Electrical Code and local amendments. When in doubt, have the design checked by a licensed electrician or engineer.