Power Calculator
Calculate electrical power, voltage, current, and resistance using Ohm's Law and power formulas. Perfect for electrical engineering and circuit analysis.
Power Calculations
Note: Provide at least 2 known values to calculate the unknown value.
Common combinations: V+I, V+R, I+R, P+V, P+I, P+R
Power Formulas
Power Formulas
- P = V × I
- P = V² ÷ R
- P = I² × R
Voltage Formulas
- V = P ÷ I
- V = √(P × R)
- V = I × R
Current Formulas
- I = P ÷ V
- I = V ÷ R
- I = √(P ÷ R)
About the Power Calculator
Our free power calculator finds power (watts), voltage, current, or resistance when you know the other two. Uses P = V × I, V = I × R, and P = I²R. Enter two values to get the third. Useful for electrical and electronics. For kVA to amps try our kVA to amps calculator; for watts to amps use our watts to amps calculator.
You may also find our kVA to amps calculator and watts to amps calculator useful.
Frequently Asked Questions
How do I calculate power from voltage and current?
Power (watts) = Voltage × Current. Enter V and I in the calculator to get P.
What is Ohm's law?
Voltage = Current × Resistance (V = I × R). With any two of V, I, R you can find the third.
AC vs DC?
This calculator uses DC/formula relationships. For AC single-phase, power factor applies; use our kVA to amps or watts to amps calculator for AC.