How to Calculate Ohm's Law
Ohm's Law states that voltage equals current times resistance. It is the most fundamental equation in electronics and electrical engineering.
The Formula
V = I x RWhere:
VVoltage — Electrical potential in voltsICurrent — Flow of charge in amperesRResistance — Opposition to flow in ohmsStep-by-Step Example
Here's how to calculate ohm's law step by step:
- 1Identify known values: Determine which two of V, I, R you already know.
- 2Choose the formula form: Use V=IR, I=V/R, or R=V/I depending on the unknown.
- 3Plug in and solve: Substitute your known values and calculate the result.
Following these 3 steps gives you the final ohm's law value.
Skip the Math
A 12V battery powering a 4-ohm speaker draws 12/4 = 3 amps of current, which helps you choose the right fuse.
Use the Free CalculatorWhy You Need This Calculation
- Ohm's Law is the foundation of electrical engineering, used in circuit design, troubleshooting, and safety calculations.
Common Mistakes
Mixing up milliamps and amps.
Convert mA to A by dividing by 1000 before calculating.
Applying Ohm's Law to non-ohmic devices.
LEDs and diodes do not follow Ohm's Law linearly.
Forgetting unit prefixes like kilo-ohms.
Convert all values to base units (V, A, ohms) first.