Tools

Ohm's law & power

Solve voltage, current, resistance, and power from any two known values.

Calculator

Ohm's law & power

Enter any two values — the other two are calculated automatically.

Voltage —
Current —
Resistance —
Power —

Formulas used

  • V = I × R
  • I = V ÷ R
  • R = V ÷ I
  • P = V × I
  • P = I² × R
  • P = V² ÷ R

Frequently asked questions

What is Ohm's law?

Ohm's law states that voltage equals current times resistance: V = I × R. Rearranged, it also gives I = V / R and R = V / I.

How do you calculate power from voltage and current?

Electrical power is the product of voltage and current: P = V × I. It can also be written P = I² × R or P = V² / R.

How many values do I need to enter?

Enter any two of voltage, current, resistance, and power, and the calculator solves the remaining two.