● Science
Ohm's law calculator
Voltage, current, resistance — pick the unknown, fill in the rest. Power dissipation included.
Result · V = I × R
12V
Power dissipation: 24 W (P = V × I)
The relationship
V = I × R — voltage equals current times resistance. From that single equation you can rearrange for any of the three. Power follows from P = V × I, which also rearranges to P = I² × R or P = V² ÷ R.
Units
- Volts (V) — electrical potential difference
- Amperes (A) — current, charge per second
- Ohms (Ω) — resistance to current flow
- Watts (W) — power, energy per second
Frequently asked questions
How do you calculate power dissipation?
P = V × I gives power in watts. You can also use P = I² × R or P = V² ÷ R when you know the resistance — all three give the same result.
What does Ohm's law actually state?
Voltage equals current times resistance: V = I × R. Given any two of the three, you can solve for the third by rearranging the equation.
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