Ohm's Law Calculator
Calculate voltage, current, or resistance using Ohm's Law. Also computes electrical power.
Examples
Find voltage: 2A through 100Ω
V = I × R = 2 × 100 = 200V
- Solve for
- Voltage (V = I × R)
- Current (I)
- 2 A
- Resistance (R)
- 100 Ω
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How It Works
Formula
Variables, symbols and units
- Voltage(V)
- Current(A)
- Resistance(Ω)
- Electrical power(W)
Calculation method explained
Select what to solve for: voltage (V=I×R), current (I=V/R), or resistance (R=V/I). Enter the two known values and the calculator finds the unknown plus the power (P=V×I).
Ohm's Law links voltage, current, and resistance with V = I × R. The calculator picks the rearranged form that matches your two knowns: voltage as a product, or current and resistance as ratios. It then multiplies voltage by current to report dissipated power. Stick to volts, amperes, and ohms so power comes out in watts directly.
References and source material
Examples
Find voltage: 2A through 100ΩVoltage (V = I × R) · 2 A → 200 V
V = I × R = 2 × 100 = 200V
- Solve for
- Voltage (V = I × R)
- Current (I)
- 2 A
- Resistance (R)
- 100 Ω
- Voltage
- 200 V
Find current: 12V across 4ΩCurrent (I = V / R) · 12 V → 12 V
I = V / R = 12 / 4 = 3A
- Solve for
- Current (I = V / R)
- Voltage (V)
- 12 V
- Resistance (R)
- 4 Ω
- Voltage
- 12 V
Find resistance: 9V at 0.5AResistance (R = V / I) · 9 V → 9 V
R = V / I = 9 / 0.5 = 18Ω
- Solve for
- Resistance (R = V / I)
- Voltage (V)
- 9 V
- Current (I)
- 0.5 A
- Voltage
- 9 V