Amps to Watts Calculator

Q: How do I convert amps to watts?

DC: Watts = Amps × Volts. Single phase AC: Watts = Amps × Volts × PF. Three phase AC: Watts = √3 × Amps × Volts × PF.

Q: What is the difference between watts and volt-amps (VA)?

Watts (W) is real power — the actual work done. VA is apparent power. W = VA × Power Factor. For resistive loads PF=1 so W equals VA, but for motors or UPS equipment the difference matters.

Convert amperes to watts and kilowatts for DC, single phase AC, and three phase AC circuits. Includes power factor for accurate real-power results.

This calculator provides estimates only. Always consult a qualified electrician for real installations.

Convert Amps to Watts

Current (Amps)

Voltage (V)

Circuit Type

Power Factor (AC only)

Result

—

Power (Watts)

—

Power (kW)

Formulas

DC:

Watts = Amps × Volts

Single Phase AC:

Watts = Amps × Volts × Power Factor

Three Phase AC:

Watts = √3 × Amps × Volts × Power Factor

Example Calculations

DC 12V Battery: 20A load on a 12V battery bank.

Watts = 20 × 12 = 240W

Single Phase 240V: 30A circuit at PF = 0.95.

Watts = 30 × 240 × 0.95 = 6,840W (6.84 kW)

Three Phase 415V: 25A per phase at PF = 0.9.

Watts = 1.732 × 25 × 415 × 0.9 = 16,165W (16.17 kW)

Practical Notes

For DC circuits (solar panels, batteries, 12/24V systems) PF is always 1 — just multiply amps × volts.
Household 120V circuits in the US: a 15A breaker delivers up to 1,800W (15 × 120).
Three phase systems deliver significantly more power for the same conductor current.
EV chargers, industrial motors, and HVAC often have PF specified on the nameplate.
The result in watts represents real (usable) power. VA would be watts ÷ PF.

Frequently Asked Questions

How do I convert amps to watts?

DC: W = A × V. Single phase AC: W = A × V × PF. Three phase AC: W = 1.732 × A × V × PF. For simple resistive loads use PF = 1.

How many watts is 10 amps at 120V?

At PF=1: 10 × 120 = 1,200W. At PF=0.9: 10 × 120 × 0.9 = 1,080W. The power factor reduces real power compared to apparent power.

What is the difference between watts and volt-amps?

Watts (W) is real power — the energy actually consumed and converted to work or heat. VA (volt-amps) is apparent power, which includes reactive power in AC circuits. W = VA × Power Factor. For a pure resistive load, W = VA. Equipment like UPS units are rated in VA because they must supply both real and reactive power.