Ohm's Law Calculator (V = R·I)
Find voltage and power from current and resistance.
Result
Voltage (V)
20.00
Power (W)
40.00
How it works
Ohm's law is the grammar of every electrical circuit: voltage equals resistance times current, U = R·I. Give this calculator a current and a resistance and it returns the voltage across the component, plus the power it dissipates, P = U·I. A water analogy makes it intuitive: voltage is the pressure pushing charge along, current is the flow rate, and resistance is the narrowness of the pipe. Double the pressure and the flow doubles; double the narrowness and it halves. The power output is what heats things. A 2 A current through 6 Ω drops 12 V and dissipates 24 W — enough to feel warm. That same relation (with P = I²·R) explains why grids transport electricity at high voltage: for the same power, higher voltage means lower current, and losses in the wires fall with the square of it.
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Frequently asked questions
What is Ohm's law?
Voltage equals resistance times current: V = R·I.
How do I find the power?
Multiply voltage by current: P = V·I, equal to R·I².
Why is electricity transported at high voltage?
Line losses are P = I²·R: they grow with the square of the current. Raising the voltage lets the same power flow with far less current, slashing the losses in the wires.
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