Electrical Power Calculator
Calculate power from voltage, current, and resistance.
This tool is for informational and educational purposes only. It is not a substitute for professional financial, medical, legal, or engineering advice. See Terms of Service.
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Enter any two of voltage, current, and resistance. Leave one field blank. The calculator computes the missing value and the power. Results update live as you type.
About Electrical Power
Electrical power measures the rate of energy conversion in a circuit. It relates to voltage, current, and resistance through several equivalent formulas: P = VI, P = I2R, and P = V2/R. Understanding electrical power is essential for sizing components, calculating energy costs, and ensuring circuit safety. Every electrical device, from a phone charger to a power plant, operates within specific power limits.
Frequently Asked Questions
What is electrical power?
Electrical power is the rate at which electrical energy is transferred in a circuit. It is measured in watts (W). Power equals voltage times current: P = V x I.
What is the relationship between power and resistance?
Power can be expressed as P = I2R (useful when current is known) or P = V2/R (useful when voltage is known). Higher resistance at constant voltage means less power dissipated.
How many values do I need to enter?
Enter any two of voltage, current, and resistance. The calculator determines the third value and computes the power.