Ohm's Law Calculator
Calculate voltage, current, or resistance using V=IR
Calculator
V = I × R = 2 A × 6 Ω = 12.0000 V
P = V × I (Watts)
Ohm's Law Formulas
- V = I × R (Voltage = Current × Resistance)
- I = V / R (Current = Voltage / Resistance)
- R = V / I (Resistance = Voltage / Current)
- P = V × I = I²R = V²/R (Power formulas)
How to Use
Calculate voltage, current, or resistance using Ohm's Law
Select what to solve
Choose whether you want to calculate voltage, current, or resistance
Enter known values
Input the two values you know (e.g., voltage and current)
View results
See the calculated value plus bonus power calculation
Ohm's Law
V = I x R
Voltage equals Current times Resistance. Rearrange to find any variable.
Frequently Asked Questions
Ohm's Law states that voltage (V) equals current (I) multiplied by resistance (R): V = IR. It is fundamental to electrical engineering and electronics, allowing you to calculate any of these three values when you know the other two. Essential for circuit design, troubleshooting, and understanding electrical systems.
To find current, rearrange the formula to I = V/R. Divide the voltage by the resistance. For example, a 12V battery across a 4 ohm resistor produces 3 amperes of current (12V / 4 ohms = 3A). Higher voltage or lower resistance means more current flow.
Power (P) in watts can be calculated using P = V x I, P = I squared x R, or P = V squared / R. Our calculator shows power alongside voltage, current, and resistance. Power tells you how much energy the circuit consumes or dissipates as heat.
Standard SI units are volts (V) for voltage, amperes (A) for current, and ohms for resistance. Power is measured in watts (W). For smaller values, use milliamps (mA = 0.001A), millivolts (mV), or kilohms (1000 ohms).