How to Calculate Power From Voltage & Currents

Knowing how much power is going to be generated is very important. If too much power is generated, the device being powered can be destroyed, while too little power will leave the device underperforming or not performing at all. Understanding how to calculate power, which equals voltage times current, will make sure the right amount of power is delivered.

Things You'll Need

• Calculator

Instructions

Calculating Power from Voltage and Current

1. Determine the voltage using a voltmeter. To use a voltmeter, insert the black probe into the positive output and the red probe into the negative output and read the display. For example, the voltmeter may read four volts.

2. Determine the current by using a multimeter. Set the multimeter to the amps function, insert the black probe into the positive output and the red probe into the negative output and read the display. For example, the multimeter may read 0.5 amps.

3. Multiply the volts by the amps. In this example, multiple four volts by 0.5 amps; the result is two watts, which is the power.

Tips & Warnings

• Make sure the units are consistent. Voltage is measured in volts, current is measured in amps, and power is measured in watts.

• Be careful not to confused kilowatts with watts. Kilowatts are one thousand watts.

References

• Ohms' Law Calculators