Ohm's Law Calculator
Use our Ohm's law calculator to calculate resistance (Ω) and power (W) from voltage (V) and current (A). Includes the Ohm's law formula, power formula, and FAQs like what is resistance in Ohm's law.
Ohm's Law and Resistance
Ohm’s law describes the relationship between voltage (V), current (I), and resistance (R) in an electrical circuit. In its simplest form, it states that voltage equals current times resistance.
Resistance is a measure of how much a material or component opposes the flow of electric current. Ohms (Ω) are the unit of resistance, so “ohms” refers to resistance.
With voltage and current, you can compute resistance and also power (the rate electrical energy is used) using standard circuit formulas.
Ohm's Law Formula and Power Formula
This calculator uses voltage and current to compute resistance and power.
V is voltage, I is current, R is resistance.
Use when voltage and current are known.
Electrical power in watts.
From voltage and current you can compute both resistance and power.
How to Calculate Ohm's Law
- 1
Enter voltage (V) in volts.
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Enter current (I) in amps.
- 3
The calculator computes resistance using R = V ÷ I.
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It computes power using P = V × I.
Frequently Asked Questions
Ohm’s law is V = I × R. Rearranged: I = V/R and R = V/I.
Yes. The ohm (Ω) is the unit of electrical resistance.
Resistance (R) is the opposition to current flow. In Ohm’s law, it links voltage and current: R = V/I.
In ideal ohmic components, resistance is approximately constant over a range of voltages and currents. In many real components (like diodes, lamps, or temperature-sensitive materials), resistance can change with conditions.
Power can be calculated as P = V × I. Using Ohm’s law, power can also be written as P = I^2 × R or P = V^2 ÷ R (not required for this calculator’s inputs).