Ohm's Law Calculator (V = IR)
Solve V = IR for voltage, current or resistance — with power dissipation as a bonus.
Result
Voltage (V)
12 V
Power dissipated
24 W
P = V × I
Concept
Ohm's Law states that the voltage across a conductor is directly proportional to the current through it, provided temperature and physical conditions remain constant — the ratio V/I is the resistance R.
Ohm's Law applies to ohmic conductors (metals at constant temperature). Non-ohmic devices like diodes, LEDs and thermistors don't follow it — their R changes with V.
Power: the rate of energy dissipation in a resistor is P = VI = I²R = V²/R. This is why high-voltage transmission lines waste less power than low-voltage ones.
Formula
V=I × R
I=VR
R=VI
P (Power)=V × I = I2 × R = V2R
Variables
VV — volts- Potential difference across the conductor.
IA — amperes- Current through the conductor.
RΩ — ohms- Resistance.
PW — watts- Power dissipated.