Ohm's Law
Ohm's law I = V / R: find current, voltage, resistance and power P = V · I = I²R = V²/R with unit conversion and a solution.
Numbers can be decimals (2.5), fractions (1/3) or scientific notation (1.5e3). Pick any units — the calculator converts them to SI.
The Ohm's law calculator finds the current, voltage or resistance of a circuit section, and the electric power in three ways. You can enter milliamps, kilovolts, kilohms and other units — the solution shows the conversion to SI, the formula and the substitution.
Ohm's law
I = U / R
The current through a circuit section is directly proportional to the voltage and inversely proportional to the resistance. Hence U = I · R and R = U / I. (In English textbooks voltage is often written V.)
Electric power
| Known | Formula |
|---|---|
| U and I | P = U · I |
| I and R | P = I² · R |
| U and R | P = U² / R |
Example 1. 12 V across a 4 Ω resistor: I = 12 / 4 = 3 A.
Example 2. A 48.4 Ω kettle on 220 V: P = 220² / 48.4 = 1000 W.
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