Volts to Watts Converter: Your Handy Calculator

This calculator applies the basic DC power formula, P = V × I: power in watts equals voltage in volts multiplied by current in amps. Enter 120 volts and 2 amps — roughly what a small space heater draws on a US household circuit — and it returns Power (W): 240.00.

Where this formula applies

P = V × I is exact for DC circuits and for AC circuits with a purely resistive load and a power factor of 1 — things like incandescent bulbs, resistive heaters, and toasters. It is not accurate for AC loads with reactance, such as motors, compressors, or switching power supplies, where real power is P = V × I × cos(θ) and the power factor (cos θ) can be well below 1. For those devices, use the nameplate wattage rather than back-calculating from voltage and current alone.

A second reference point

A typical US wall outlet supplies 120 V. A device drawing 5 A from that outlet — near the upper end of what a standard 15-amp circuit allows — is consuming 120 × 5 = 600.00 watts. Comparing that number against a device's rated wattage is a quick way to check whether your current reading is in the expected range.

Amps from watts, the other direction

If you know a device's wattage and voltage instead of its current, divide watts by volts to get amps (I = P / V) — this calculator only performs the forward calculation (V × I → W), not the reverse.