Amps to watts calculator
Convert amps to watts for DC, single-phase AC, and three-phase AC systems.
What this calculator covers
Use this calculator when you know current and voltage and want the real power draw in watts.
For AC loads, power factor matters because not all apparent power becomes useful work. The calculator keeps that distinction explicit instead of hiding it behind a single conversion factor.
Frequently asked questions
- Why can't I just multiply amps by volts for AC circuits?
- Voltage times current gives apparent power (volt-amps), not real power (watts). For AC loads the power factor — a value between 0 and 1 — reduces apparent power to the actual usable wattage, so the two figures differ whenever the power factor is below 1.
- What power factor should I use if I don't know mine?
- A power factor of 0.9 is a common default for typical residential and light commercial loads. Purely resistive loads like heaters and incandescent bulbs have a power factor of 1.0. Check the equipment nameplate or datasheet for a more accurate value.
- When does the three-phase formula apply?
- Use the three-phase setting when your circuit supplies a three-phase load and the current figure is a per-phase (line) ampere reading. The calculator multiplies by the square root of 3 to account for the line-to-line voltage relationship in balanced three-phase systems.
- What is kilowatts in the result and why is it shown?
- Kilowatts is simply the watt result divided by 1,000. It is included because equipment ratings, utility bills, and service-panel sizing are often stated in kilowatts or kilowatt-hours rather than watts.
Tool
Run the calculation
Result
RESULT · WATTS
â„–196
Primary result
1,620.00 W
15.00 A at 120.00 V in AC single-phase mode equals 1,620.00 W.
- Watts
- 1,620.00 W
- Kilowatts
- 1.6200 kW
- System type
- AC single-phase
- Power factor used
- 0.900
Step-by-step solution
- 1.Choose the formula for the selected system type: W = V x I x PF.
- 2.Use a power factor of 0.900.
- 3.Multiply voltage and current, then apply the AC power-factor and three-phase adjustment if needed to get watts and kilowatts.
Walkthrough
Visual walkthrough
Converting amps to watts starts with voltage and then adds power-factor and three-phase adjustments only when the electrical system needs them.
01
Start with current and voltage
120.00 V x 15.00 A
DC and AC single-phase both begin with the same voltage-times-current foundation.
02
Apply AC adjustments when needed
W = V x I x PF
Power factor reduces real power for AC loads, and three-phase systems add the sqrt(3) line-to-line adjustment.
03
Read the power result
The primary output is watts, with kilowatts included for equipment and service-size comparisons.
1,620.00 W