Kerova

Calculator · General electrical

Ohm's law and power calculator

Choose which two values you know, enter them, and get the other two, with the working. Enter current in milliamps or amps.

Your figures

Enter current in
V
mA

Result

Enter the two values to see the result.

Working

V = I × R · P = V × I

  • V is voltage in volts. I is current in amps. R is resistance in ohms. P is power in watts.
  • V = I × R, and P = V × I. The other forms come from putting those two together.
  • For a battery, current times hours gives amp hours. For a cable, use the voltage drop calculator.

For guidance only. Always check against the current edition of the standard and the manufacturer's data.

Built by the engineer behind Kerova, certificate software for fire and security firms.