Watts to Amps Calculator
Convert electrical power in watts to current in amps for DC, single-phase AC and three-phase AC circuits.
Current
How we calculated it
About the Watts to Amps Calculator
Electrical power does not translate into current until voltage—and for many AC loads, power factor and phase—are known. This calculator solves that relationship for DC and supported AC circuits.
Current calculations should not be used by themselves to select wiring, breakers or protective devices for safety-critical work. Equipment startup current, continuous-load rules and local electrical requirements can all matter.
How to Use the Watts to Amps Calculator
- Enter the power in watts or kilowatts from the equipment rating.
- Enter the circuit voltage and select the correct AC or DC mode.
- For AC loads, enter power factor when the calculator requires it rather than assuming every load has a power factor of 1.
- Calculate the current, then compare it with equipment documentation and applicable electrical design requirements.
How the Calculation Works
For DC or a unity-power-factor single-phase load, current I = power P ÷ voltage V. In single-phase AC with power factor PF, I = P ÷ (V × PF).
Three-phase power uses the appropriate phase relationship, commonly I = P ÷ (√3 × V × PF) when line-to-line voltage is used. Units are normalized before division.
Worked example
Watts to Amps Calculator Worked Example
1,200 W appliance on 120 V
For a simple unity-power-factor relationship, current = 1,200 ÷ 120 = 10 A. If an AC load has a lower power factor, the current needed for the same real power can be higher.
Result guide
Understanding Your Watts to Amps Calculator Result
The calculated amperage is the current implied by the entered electrical relationship. Actual equipment can draw more during startup or under different operating conditions.
Before you rely on the answer
Assumptions and Limitations
- The voltage is the correct operating voltage for the load.
- The selected circuit type and phase relationship are correct.
- Power factor is entered where required and startup/surge current is handled separately.
Practical tip
Using This Result in Practice
Use nameplate or manufacturer data when available. For motor, compressor or large AC loads, current calculated from watts alone is not a substitute for the manufacturer’s rated current and installation instructions.
Related calculations
Useful Calculations to Continue With
If you know volts and amps and want power instead, use the Electrical Power Calculator.
If you are evaluating a long cable run, use the Voltage Drop Calculator separately because acceptable conductor sizing depends on more than current alone.
Common questions
Watts to Amps Calculator FAQ
How many amps is 1,000 watts at 120 volts?
With the simple DC or unity-power-factor relationship, 1,000 ÷ 120 ≈ 8.33 A.
Why does power factor change amps?
For AC loads, real power can be lower than apparent power. A lower power factor means more current may be required to deliver the same real wattage.
Can I size a breaker from this result?
Not safely from this number alone. Breaker and conductor selection must account for equipment ratings, continuous loads, startup current and applicable electrical rules.