How to use the Ohm's Law Calculator
The Formula
Voltage (V) equals current (A) times resistance (Ω): V = I × R. Rearrange to find current (I = V ÷ R) or resistance (R = V ÷ I). Enter exactly two known values and leave the third empty.
Practical Example
Use Ohm's law for DC circuits, LED resistor sizing, fuse checks, and quick bench calculations. For power in watts, pair with the Watts to Amps or Volts to Watts calculators.
About Ohm's Law Calculator
Ohm's law formula
Voltage (V) equals current (A) times resistance (Ω): V = I × R. Rearrange to find current (I = V ÷ R) or resistance (R = V ÷ I). Enter exactly two known values and leave the third empty.
When to use this tool
Use Ohm's law for DC circuits, LED resistor sizing, fuse checks, and quick bench calculations. For power in watts, pair with the Watts to Amps or Volts to Watts calculators.
Frequently asked questions
Q: How many values do I need? A: Exactly two—leave the unknown blank. Q: Does this work for AC? A: It applies to resistive AC loads; reactive loads need impedance, not just R.