Watts to Amps at 120V
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At 120 V DC, amps = watts ÷ 120. A 1,500 W load draws 12.50 A. Divide any wattage by 120 to get the current at this supply voltage. Use the calculator below for AC circuits and power factor.
How do you convert watts to amps?
To convert watts to amps, divide watts by volts. For example, a 1500 W heater on a 120 V circuit draws 1500 ÷ 120 = 12.5 amps; on a 240 V circuit the same 1500 W draws 1500 ÷ 240 = 6.25 A. For AC circuits, also divide by the power factor: A = W ÷ (V × PF).
Watts to Amps Conversion Table (DC)
Watts to Amps Formula
In practice: the 80% rule on a 120 V circuit
North American general-purpose circuits are 15 A or 20 A at 120 V, giving hard ceilings of 1,800 W and 2,400 W. Anything drawing for three hours or more counts as continuous and is limited to 80% of the breaker, which drops those ceilings to 1,440 W and 1,920 W. Most household overload problems trace back to treating the nameplate maximum as the usable budget rather than the derated figure.
Frequently Asked Questions
Divide the power in watts by the voltage in volts. For DC circuits: A = W ÷ V. For AC single-phase circuits, also divide by the power factor: A = W ÷ (V × PF). For AC three-phase: A = W ÷ (V × PF × 1.732).
DC: A = W ÷ V. AC Single-phase: A = W ÷ (V × PF). AC Three-phase: A = W ÷ (V × PF × 1.732). PF is the power factor — a value between 0 and 1 that accounts for reactive power in AC circuits. DC circuits always have a power factor of 1.
It depends on voltage and circuit type. 120V DC: 12.5 A. 240V DC: 6.25 A. 120V AC single-phase (PF 0.8): 15.625 A. 240V AC single-phase (PF 0.8): 7.8125 A.
Watts (W) measure electrical power — the rate at which energy is consumed or produced. Amps (A) measure electric current — the rate at which electric charge flows through a conductor. The two are linked by voltage: W = A × V. A device can draw few amps at high voltage or many amps at low voltage while consuming the same wattage.