Voltage, Current & Resistance Calculator
Solve any one of voltage, current or resistance from the other two using Ohm’s law, with power included.
How it works
V = I·R · I = V/R · R = V/I · P = V·I
Ohm’s law ties voltage, current and resistance together: the voltage across a resistor equals the current through it times its resistance. Rearranging lets you find any one quantity from the other two. Multiply voltage by current and you get the power the resistor turns into heat. This calculator picks the right form automatically and refuses to divide by zero.
Worked example
Solving for voltage with I = 2 A through R = 6 Ω gives V = 2 × 6 = 12 V, and the resistor dissipates P = 12 × 2 = 24 W.
Sources: Ohm’s law — Wikipedia
Frequently asked questions
Which quantities do I need to enter?
Any two of the three. Choose what to solve for, and enter the other two values; the calculator applies the matching form of Ohm’s law and also reports the power.
Does Ohm’s law always hold?
It holds for ohmic components like resistors and most wires, where current is proportional to voltage. Diodes, lamps and semiconductors are non-ohmic — their resistance changes with conditions — so the law is only a local approximation for them.
How is power related?
Power is the rate energy is converted to heat, P = V·I. Combined with Ohm’s law it can also be written P = I²R or P = V²/R, all giving the same watts.
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