Motor Full-Load Current Estimator
FLC from nameplate power for DC, single and three-phase motors — with efficiency, power factor and DOL starting current.
For sizing contactors, overloads and cable, codes require the TABLE current (NEC 430) rather than a calculation — use this estimate for sanity checks and energy math. Starting inrush of 5–8× FLC lasts a few seconds: breakers need motor-rated (D-curve) characteristics, and generators need ~3× the motor kVA to start it direct-on-line.
Motor Current Estimator computes full-load current from a motor's power rating, voltage, efficiency and PF — free, instant and private in your browser. Electricians sizing contactors and cable, and engineers checking generator/inverter headroom use it to skip the datasheet algebra: type your numbers, read the answer with the substituted formula shown step by step, and share an exact permalink of the calculation.
About Motor Full-Load Current Estimator
Motor Current Estimator computes full-load current from a motor's power rating, voltage, efficiency and PF using the standard engineering relation: I = P/(√3·V·η·PF) for 3φ; drop the √3 for single-phase, drop PF for DC. Worked live: a 2.2 kW, 415 V three-phase motor at η 88 %, PF 0.85 draws about 4.1 A — and ~25 A starting DOL. The result recalculates on every keystroke, the worked-example panel shows your numbers substituted into the formula, and the Copy permalink button encodes the inputs in the URL so a colleague opens exactly your calculation. Everything runs client-side — nothing you type leaves your device.
How to use Motor Full-Load Current Estimator
- 1Enter your values — the tool starts with realistic defaults for this exact use case, so the worked example is meaningful immediately.
- 2Read the live result and the worked-example panel, which substitutes your numbers into the formula step by step.
- 3Adjust any input to compare scenarios, then use Copy result or Copy permalink to share the calculation.
Why use Motor Full-Load Current Estimator?
- ✓Implements the real formula — I = P/(√3·V·η·PF) for 3φ — with the substitution shown, not a black box
- ✓Built for electricians sizing contactors and cable, and engineers checking generator/inverter headroom
- ✓Copy result and permalink buttons — share the exact calculation in a README, forum answer or design review
- ✓100% free, no sign-up, runs entirely in your browser (works offline once loaded)
Frequently asked questions
How do you calculate motor current?+
Full-load current from a motor's power rating, voltage, efficiency and PF follows I = P/(√3·V·η·PF) for 3φ; drop the √3 for single-phase, drop PF for DC. For example, a 2.2 kW, 415 V three-phase motor at η 88 %, PF 0.85 draws about 4.1 A — and ~25 A starting DOL. The calculator applies the same relation and shows the substituted arithmetic so you can verify every step.
Why is starting current so much higher than running current?+
At standstill an induction motor is essentially a transformer with a shorted secondary — 5–8× FLC flows until it spins up. Breakers need motor (D-curve) characteristics, soft-starters/VFDs tame it, and generators need ~3× the motor kVA to start one DOL.
Can I use this estimate for code compliance?+
No — wiring codes (e.g. NEC Article 430) require their TABLE currents for conductor and overload sizing regardless of nameplate. Use this estimator for sanity checks, energy math and non-code engineering; use the table for the inspection.
Is the Motor Current Estimator free and private?+
Yes — completely free with no sign-up or usage limits, and it runs entirely in your browser: the values you enter are never uploaded or stored on a server.
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