This Ohm's law calculator relates voltage, current, and resistance for basic DC circuit estimates.
Physics
Ohm's Law Calculator
Solve Ohm's law relationships among voltage, current and resistance.
Calculator
About this calculator
Formula notes
The core relationships are V = I x R, I = V / R, and R = V / I.
Worked examples
- Example: 12 V across 4 ohm draws 3 A, because I = 12 / 4 = 3.
- A 12 V supply across a 6 ohm resistor gives 2 A and dissipates 24 W under the ideal resistive model.
How to use it
- Enter any two known values among voltage, current, and resistance.
- Solve for the remaining quantity.
- Keep units consistent before interpreting the result.
Frequently asked questions
Does this cover AC impedance?
This page is for basic Ohm's law relationships. AC circuits with reactance need a broader model.
Why can measured resistance change when a component heats up?
Many materials have temperature-dependent resistivity. Ohm's law may still apply at each operating point, but R is no longer constant.
Limits and interpretation
- Ohm's law in this form assumes an ohmic element at a stable operating condition; semiconductors, lamps, batteries, and reactive circuits may be nonlinear.
- Calculated power does not establish component rating, thermal design, wire size, protection, isolation, or electrical safety.