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Ohm’s Law Calculator
Enter any two of voltage, current and resistance to find the rest and power.
Power
—
Fill any two.
| Voltage | — |
|---|---|
| Current | — |
| Resistance | — |
| Solved for | — |
Show our math
Enter your figures above to see the step-by-step working.
Everything computed client-sideEverything computed client-side — nothing leaves this page
How the Ohm’s Law Calculator Works
Ohm’s law ties together the three basics of an electrical circuit: voltage (V), current (I) and resistance (R), through V = I × R. Enter any two and this calculator finds the third, then works out the power dissipated, P = V × I.
So 12 volts across a circuit drawing 2 amps means a resistance of 6 ohms and 24 watts of power. It’s the workhorse equation of electronics, useful for sizing resistors, checking loads and understanding circuits.
V = I × R · P = V × I
Frequently Asked Questions
What is Ohm’s law?
A rule stating that voltage equals current times resistance (V = IR). Rearranged, it also gives current (V/R) or resistance (V/I).
How do you calculate power from Ohm’s law?
Power is voltage times current (P = VI). You can also write it as I²R or V²/R.
What are the units?
Voltage in volts (V), current in amperes (A), resistance in ohms (Ω) and power in watts (W).
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