Convert amps or milliamps to watts, kilowatts, VA, kVA, and VAR for DC, single-phase AC, or balanced three-phase AC.
Calculator
Amps to Watts Results
Review the converted result, power components, formula inputs, and common-voltage comparisons.
Power and Current Components
Calculation Details
| Metric | Value | Note |
|---|
Power at Common Voltages
Uses the entered real power or current and AC power factor. Each row changes the system and voltage.
| System | Voltage | Result | Kilowatts |
|---|
Convert amps or milliamps to watts
Current alone does not determine power. Enter amps or milliamps, voltage, and the correct DC, single-phase, or balanced three-phase relationship. For AC, enter a power factor from greater than 0 through 1. The calculator reports real power in watts and kilowatts, apparent power in VA and kVA, and simplified reactive power in VAR.
DC: W = A x V
single phase: W = A x V x PF
three phase, line-to-line: W = √3 x A x VLL x PF
three phase, line-to-neutral: W = 3 x A x VLN x PF
Amps-to-watts examples
Fifteen amps at 120 V DC or single-phase AC with power factor 1 equals 1,800 W. Ten amps at 120 V equals 1,200 W, and 2 A at 120 V equals 240 W. A balanced three-phase load drawing 10 A at 208 V line-to-line and 0.9 power factor uses about 3,242 W of real power and 3,603 VA.
Three-phase voltage type
Use the line-to-line option when the entered voltage is measured between two phase conductors. Use line-to-neutral when the voltage is measured from one phase to neutral in a balanced wye system. The multipliers differ: √3 for line-to-line voltage and 3 for line-to-neutral voltage.
For a 120/208 V system, 208 V line-to-line and 120 V line-to-neutral describe the same nominal system. Matching each voltage to the correct formula produces nearly the same total three-phase power.
Real, apparent, and reactive power
Apparent power depends on RMS current, RMS voltage, and the selected phase relationship. Real power equals apparent power times power factor. Reactive power is the remaining power-triangle component in this simplified sinusoidal model. At power factor 1, watts equal VA and reactive power is zero.
The US Department of Energy's industrial electrification framework uses P = √3 x voltage x current x power factor for typical balanced three-phase loads using line-to-line voltage.
Reference power at common voltages
The comparison table applies the entered current and power factor to common DC, US single-phase, and three-phase voltages. These are mathematical reference scenarios, not equipment operating recommendations.
Breaker rating is not measured current
A 20 A breaker does not mean a load continuously draws 20 A. Use measured current or equipment data, and verify conductor, protection, duty, starting current, and equipment-specific requirements separately.
Frequently asked questions
How many watts is 15 amps?
At 120 V DC or single-phase AC with power factor 1, 15 A equals 1,800 W. At 240 V it equals 3,600 W. Other systems and power factors produce different results.
Can I enter milliamps?
Yes. Select mA and enter the value directly; the calculator divides it by 1,000 before calculating power.
Why does a lower power factor reduce watts?
For fixed RMS voltage and current, apparent power stays the same while a smaller share becomes real power.
Can this calculate energy use?
No. Watts measure power. Multiply kilowatts by operating hours to estimate kilowatt-hours of energy.
How do I calculate current from watts?
Use the watts to amps calculator with matching voltage, system type, and power factor.