Motor power to current calculator
Convert motor power in kW or horsepower to full-load current for three-phase, single-phase and DC motors — or run it in reverse and estimate shaft power from a measured current.
Motor power to current (3-ph / 1-ph / DC)
Motor type
Three-phase: I = (kW × 1000) / (√3 × V × PF × η) · single-phase: I = (kW × 1000) / (V × PF × η) · DC: I = (kW × 1000) / (V × η). Reverse: enter a measured current below to estimate the shaft power.
Reverse — current to motor power
Full-load current is what a contactor, breaker, thermal overload relay or drive must be sized for — motors draw 5–8× FLA on startup, so protective devices are selected at or above the nameplate current. AO Ctrl stocks the switching, protection and drive hardware:
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AO Ctrl provides this tool for reference only.
Frequently asked questions
How do I convert motor kW to current?
For a three-phase motor I = (kW × 1000) / (√3 × V × PF × η). A single-phase motor uses I = (kW × 1000) / (V × PF × η), and a DC motor I = (kW × 1000) / (V × η). Use the nameplate voltage, efficiency and power factor — a typical 11 kW, 400 V motor with η 0.90 and PF 0.85 draws about 20.8 A.
How do I convert horsepower to amps?
Convert horsepower to watts first: 1 hp = 745.7 W. A 15 hp, 460 V three-phase motor at η 0.90 and PF 0.85 draws about 15 × 745.7 / (√3 × 460 × 0.90 × 0.85) ≈ 18.4 A. Many NEC tables quote 21 A at 460 V because they use a slightly lower assumed efficiency.
Can I estimate motor power from measured current?
Yes — the reverse calculation uses the same equations solved for power: P (kW) = √3 × V × PF × η × I / 1000 for three-phase, with the single-phase and DC variants shown above. This is only an estimate because current, efficiency and power factor all change with load.
AO Ctrl provides this tool for reference only.