Ohm's Law Calculator (V, I, R, P)
Enter any two of voltage, current, resistance and power — get the other two with the substituted formula shown step by step.
Ohm's law applies to LINEAR resistances — LEDs, diodes and lamps don't obey it (a cold lamp filament reads ~10× lower than running resistance). The power result tells you the resistor rating: run parts at ≤ 50 % of rated wattage for longevity.
Ohm's Law Calculator computes any two of voltage, current, resistance and power solved for the other two — free, instant and private in your browser. Students, electricians and engineers — the four-quantity wheel everyone reaches for use it to skip the datasheet algebra: type your numbers, read the answer with the substituted formula shown step by step, and share an exact permalink of the calculation.
About Ohm's Law Calculator (V, I, R, P)
Ohm's Law Calculator computes any two of voltage, current, resistance and power solved for the other two using the standard engineering relation: V = I·R and P = V·I = I²R = V²/R. Worked live: 12 V across 24 Ω drives 0.5 A and dissipates 6 W. The result recalculates on every keystroke, the worked-example panel shows your numbers substituted into the formula, and the Copy permalink button encodes the inputs in the URL so a colleague opens exactly your calculation. Everything runs client-side — nothing you type leaves your device.
How to use Ohm's Law Calculator (V, I, R, P)
- 1Enter your values — the tool starts with realistic defaults for this exact use case, so the worked example is meaningful immediately.
- 2Read the live result and the worked-example panel, which substitutes your numbers into the formula step by step.
- 3Adjust any input to compare scenarios, then use Copy result or Copy permalink to share the calculation.
Why use Ohm's Law Calculator (V, I, R, P)?
- ✓Implements the real formula — V = I·R and P = V·I = I²R = V²/R — with the substitution shown, not a black box
- ✓Built for students, electricians and engineers — the four-quantity wheel everyone reaches for
- ✓Copy result and permalink buttons — share the exact calculation in a README, forum answer or design review
- ✓100% free, no sign-up, runs entirely in your browser (works offline once loaded)
Frequently asked questions
How do you calculate ohm's law?+
Any two of voltage, current, resistance and power solved for the other two follows V = I·R and P = V·I = I²R = V²/R. For example, 12 V across 24 Ω drives 0.5 A and dissipates 6 W. The calculator applies the same relation and shows the substituted arithmetic so you can verify every step.
Does Ohm's law apply to LEDs, diodes and bulbs?+
No — those are non-linear. A diode's current rises exponentially with voltage, and a lamp filament's resistance grows ~10× as it heats. Ohm's law holds for resistors and approximately for wires; everything else needs its I-V curve.
Which power formula should I use — VI, I²R or V²/R?+
They're identical when all three quantities belong to the SAME element. Errors come from mixing — using the supply voltage with one resistor's current in a chain. Identify the element, take ITS V and I, and any form works.
Is the Ohm's Law Calculator free and private?+
Yes — completely free with no sign-up or usage limits, and it runs entirely in your browser: the values you enter are never uploaded or stored on a server.
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