Watts Calculator
Calculate watts from volts and amps, or using resistance. Supports P = V × I, P = I²R, and P = V²/R formulas.
Power— W
How to Calculate Watts
P = V × I
Power (watts) equals voltage (volts) multiplied by current (amps). This is the most common formula for calculating electrical power.
Alternative Formulas
P = I² × R | P = V² / R
When resistance is known, you can calculate power using current squared times resistance, or voltage squared divided by resistance.
Example:
A 120V circuit drawing 10A:
P = 120 × 10 = 1,200 watts
A 120V circuit drawing 10A:
P = 120 × 10 = 1,200 watts
FAQ
What is a watt?
A watt (W) is the SI unit of power. It represents the rate of energy transfer — one watt equals one joule per second.
How do watts relate to kilowatts?
1 kilowatt (kW) = 1,000 watts. Kilowatts are commonly used for larger appliances and electricity billing.
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Last updated: 2026-08-08