Ohm's Law Calculator
Solve volts, amps, ohms, and watts from any two of V, I, and R, or from power plus one of those. Informational, not wiring or code approval.
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How to use Ohm's law calculator
- Enter any two of volts, amps, and ohms. Leave the unknown blank. Do not type 0 unless 0 is a real value.
- Or enter watts plus one of volts, amps, or ohms, and leave the rest blank.
- Read volts, amps, ohms, and watts. The page uses V = I R and P = V I.
- Treat the figures as arithmetic, not wiring or code approval. Nothing is uploaded.
Ohm's law
V = I R with P = V I
| Voltage | Electric potential difference in volts |
|---|---|
| Current | Electric current in amperes |
| Resistance | Opposition to current in ohms |
| Power | P = V I in watts |
| Solve rule | Any two of V, I, R, or power plus one of those three |
| Approval | Informational. Not wiring or code approval. |
What Ohm's law computes
Ohm's law states V = I R. Power on this page is P = V I. Enter any two of volts, amps, and ohms, or enter watts plus one of those three. The page fills the missing values. The default 12 V and 2 A gives 6 ohms and 24 W.
Voltage, current, resistance, and power
Voltage is potential difference. Current is charge flow. Resistance is how much a path opposes that flow. A watt is a joule per second. This page keeps those four quantities on one form so you do not mix them with conductor size or voltage drop.
How this page solves the set
If volts and amps are known, ohms is V / I and watts is V times I. If amps and ohms are known, volts is I times R. If you supply watts and volts, amps is P / V. If you supply watts and ohms, amps is the square root of P / R. Blanks are missing values. The work runs in this tab.
Limits
The model is a single DC resistance. It ignores temperature, AC impedance, and wire ampacity. Informational, not wiring or code approval. CZNull does not receive the numbers. See the disclaimer.