Ohm's Law Calculator

Enter any 2 values then click "Calculate". The unknown values will be calculated.

Voltage millivolts volts kilovolts megavolts
Current milliamps amps kiloamps megaamps
Resistance milliohms ohms kilohms megaohms
Power milliwatts watts kilowatts megawatts

Ohm's Law defines the relationship between power, voltage, current, and resistance. The various possible formulas for Ohm's law are as follows.

P = power in watts
E = voltage in volts
I = current in amps
R = resistance in ohms

P = E2/R
P = I2 * R
P = E * I

E = sqrt(P * R)
E = P/I
E = I * R

I = E/R
I = P/E
I = sqrt(P/R)

R = E/I
R = E2/P
R = P/I2