How to Calculate Watts From Volts

Power is measured in watts.

Watts (W) are a metric unit used to measure power, with one watt equaling a joule per second. Volts are a measure of electromotive force. You can only calculate watts from volts if you also know the number of amps. Amps are a measure of resistance in the circuit. The higher the resistance, the greater the number of volts. You may want to determine the number of watts from the number of volts and amps for building an electrical circuit.

Things You'll Need

• Amp meter

Instructions

1. Determine the number of volts that you are trying to convert to watts and call it V. For example, if the problem states that you have 120 volts, you would use 120 for V.

2. Measure the number of amps in the circuit using an amp meter and call the result A. For example, if you got a reading of 5 amps, you would use 5 for A.

3. Multiply the number of volts (V) by the number of amps (A) to calculate the number of watts (W). For example, if you have 120 volts and 5 amps, you would multiply 120 by 5 to get 600 watts.

References

• SI Metric: Converting Watts Amps Volts
• Bug Club: Electrical & Electronics, Ohm's Law, Formulas & Equations