Ohm's Law Calculator
Solve for voltage, current, resistance, or power — enter any two values
Solve For
Voltage (V)
V
Ohm's Law Triangle
V = I × R
I = V / R
R = V / I
P = V × I = I² × R = V² / R
All Values
Voltage
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Current
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Resistance
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Power
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Ohm's Law Explained
Ohm's Law states that the current through a conductor is directly proportional to the voltage across it and inversely proportional to the resistance: V = I × R. It's the foundational relationship in electronics, named after German physicist Georg Ohm (1827).
The power formula P = V × I extends Ohm's Law. Combining with V = IR gives P = I²R (for heating calculations, like how much heat a resistor dissipates) and P = V²/R (for power loss in wires). These are used in circuit design, electrical safety, and energy efficiency calculations.
lightbulb Example
Car battery: 12V, 60W headlight:
1I = P/V = 60/12 = 5 A
2R = V/I = 12/5 = 2.4 Ω
✓ Two headlights draw 10A from a 12V battery