Electrical Load Calculator (Watts to Amps)
Home & DIY· 5 toolsFree watts-to-amps calculator. Single-phase (US 120 V / 240 V residential): I = W / V. Three-phase (commercial 208 V / 480 V): I = W / (V × √3 × power factor). Outputs the line current and the recommended breaker size using the NEC 80% continuous-load rule (continuous load ≤ 80% of breaker rating).
Single-phase · I = W / V
Three-phase · I = W / (V × √3 × pf)
NEC 80% rule · Continuous load ≤ 80% of breaker rating. Breaker amps = load / 0.8.
Safety: This calculator is for estimation. Final circuit design, breaker selection, and wire sizing must be done by a licensed electrician per local code (NEC / CEC) and the equipment manufacturer's nameplate ratings.
Frequently Asked Questions
Frequently Asked Questions
References
References and sources
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