Watts to Amps Calculator
Convert watts to amps — or amps to watts — for DC, AC single-phase, and AC three-phase circuits, with power factor handled properly. The conversion the back of every appliance label assumes you know.
1.0 resistive · 0.8–0.95 motors.
Current draw
0 A
A = W ÷ (V × PF)
Estimates for planning only. Always verify against your local electrical code and consult a licensed electrician before sizing circuits.
How the watts–amps conversion works
Three formulas, picked automatically by current type: DC: A = W ÷ V. AC single-phase: A = W ÷ (V × PF). AC three-phase: A = W ÷ (1.732 × V × PF), where 1.732 is √3. Going the other way (amps to watts) just inverts them. The power factor matters for motors and compressors — at PF 0.8, the same watts pull 25% more amps than a resistive load, and your wiring must carry the amps.
The "breaker fit" chip applies the common 80% continuous-load rule to standard breaker sizes, a quick sanity check — not a substitute for code compliance.
Watts to amps FAQ
How do I convert watts to amps?
DC or resistive AC: amps = watts ÷ volts (1,200 W on 120 V = 10 A). AC with power factor: amps = watts ÷ (volts × PF). Three-phase: amps = watts ÷ (1.732 × volts × PF).
What is power factor and when do I need it?
The ratio of real to apparent power in AC circuits. Resistive loads (heaters, kettles) are ~1.0; motors and compressors run 0.7–0.95. Lower PF means more amps for the same watts.
How many amps is 1500 watts?
12.5 A on 120 V — why a space heater nearly fills a 15 A circuit — or about 6.5 A on 230 V. Continuous loads should stay at or below 80% of the breaker rating.
Why does three-phase use a 1.732 factor?
1.732 is √3. In a balanced three-phase system, power = √3 × line voltage × line current × PF, so current = watts ÷ (√3 × volts × PF).