Ohm's Law Calculator
Calculate voltage, current, resistance, or power from any two known values.
I want to calculate:
Enter any two of the three values below:
A
Ω
W
Ohm's Law Triangle
P = V × I
P = I² × R
P = V² / R
V = √(P × R)
Result
--
Enter two values to calculate
Common Values
LED2V / 20mA
USB Port5V / 500mA
Car Battery12V / -
Household (US)120V / -
Household (EU)230V / -
Understanding Ohm's Law
Ohm's Law is the fundamental relationship in electrical circuits, stating that the voltage (V) across a conductor is directly proportional to the current (I) flowing through it, with the constant of proportionality being the resistance (R): V = I × R.
The Four Quantities
- Voltage (V): Measured in Volts (V). The electrical pressure or potential difference that drives current through a circuit.
- Current (I): Measured in Amperes (A). The flow rate of electric charge through a conductor.
- Resistance (R): Measured in Ohms (Ω). The opposition to current flow in a circuit.
- Power (P): Measured in Watts (W). The rate at which electrical energy is consumed or produced.
Key Formulas
- V = I × R (Voltage = Current × Resistance)
- I = V / R (Current = Voltage / Resistance)
- R = V / I (Resistance = Voltage / Current)
- P = V × I (Power = Voltage × Current)
- P = I² × R (Power = Current² × Resistance)
- P = V² / R (Power = Voltage² / Resistance)