Ohm's Law Calculator
Calculate voltage, current, resistance, or power from any two of the four.
Result
Voltage (V)
12 V
Current (A)
2 A
Resistance (Ω)
6 Ω
Power (W)
24 W
Usage examples
Checking the current flowing in a circuit
Given the supply voltage and a resistor's value, instantly find the current flowing and the power being consumed.
Working backward to find a needed resistor value
Set a target current and voltage, then calculate the resistance a circuit needs to achieve it.
Checking a component's power dissipation
Calculate the power a component dissipates from its current and resistance, so you can pick a part with an adequate wattage rating.
Frequently asked questions
Is what I enter sent to a server?
No. All calculations happen entirely in your browser and are never sent to a server.
Can I enter negative numbers or zero?
Voltage, current, resistance, and power are treated as non-negative values here, and a value of zero used in a division can't be calculated.
Does this work for AC circuits?
This calculator uses the basic Ohm's law relationships, which assume DC or a purely resistive load. For AC circuits involving impedance and power factor, additional calculations are needed.
Which values should I enter?
Pick the pair of values you already know from the tabs, enter them, and the other two values are calculated automatically.