Volts, amps and watts calculator
Calculator
The calculator needs JavaScript. The tables below give the same numbers for common cases.
How it is worked out
- P = V × I (DC, or AC at power factor 1).
| Inputs | Answer |
|---|---|
| Find: Watts (from volts and amps); Volts: 120; Amps: 10; Watts: 1200 | 120 V × 10 A = 1,200 W. |
| Find: Amps (from watts and volts); Volts: 230; Amps: 5; Watts: 2300 | 2,300 W ÷ 230 V = 10 A. |
| Find: Volts (from watts and amps); Volts: 12; Amps: 3; Watts: 36 | 36 W ÷ 3 A = 12 V. |
How to use it
Power (watts) equals voltage (volts) times current (amps): P = V × I. Rearranged, amps = watts ÷ volts and volts = watts ÷ amps. These relations hold for DC and for AC resistive loads; reactive loads need the power factor.
Use the watts-to-amps and amps-to-watts calculators for single-phase and three-phase AC with a power factor.
Frequently asked questions
How do I find watts from volts and amps?
Multiply them.
How do I find amps from watts and volts?
Divide watts by volts.
How do I find volts?
Divide watts by amps.
Method: standard arithmetic shown step by step; no outside data is used. Checked 2026-11-12.
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General information only. Results are plain arithmetic on the numbers you enter; check anything important (money, health, school work) against your own records or the official source.