Watt Calculator
Use our watt calculator to calculate electrical power (watts) from voltage and current. Includes Watt’s law, voltage and watts explained, how to figure watts step by step, and answers about volts vs watts and whether watts can be converted to volts.
Voltage and Watts Explained
A watt (W) is the unit of electrical power—how fast energy is being used or produced.
Watts are not the same as volts. Volts (V) measure electrical potential (pressure), amps (A) measure current (flow), and watts (W) measure power (how much work electricity is doing).
This watt calculator helps you calculate watts from voltage and current using Watt’s law.
Watt’s Law Formula
Watt’s law relates electrical power to voltage and current.
Power (watts) equals voltage multiplied by current.
A device drawing 2 amps at 120 volts uses about 240 watts.
How to Calculate Watts
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Enter the voltage (V).
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Enter the current (A).
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Multiply voltage by current to get watts: W = V × A.
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Use the result to estimate power usage, load sizing, or device consumption.
Frequently Asked Questions
No. Volts measure electrical potential (pressure), while watts measure electrical power. You need voltage and current (amps) to calculate watts.
Use Watt’s law: watts = volts × amps.
Not by itself. To find volts, you need either current or resistance. From Watt’s law, V = W ÷ A if you know amps.
Watts don’t convert to volts directly because they measure different things. If you know current, you can compute volts as V = W ÷ A.
You need current (amps). Power is P = V × I. Without amps, you can’t determine watts from voltage alone.
The SI unit of power is the watt (W).
Current to watts means calculating power using current and voltage: watts = amps × volts.