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Calculators / Science / Ohm’s law
Ohm’s law calculator
Find current and power from voltage and resistance.
On this page
Current0.12A
Power1.44W
Calculator controls
How to calculate
Find current and power from voltage and resistance.
Current = voltage ÷ resistance; power = voltage² ÷ resistance
Worked example
Voltage (V): 12; Resistance (Ω): 100.
Current: 0.12 A; Power: 1.44 W.
Assumptions and limits
Ideal DC resistive circuit. Not a safety or component-rating assessment.
Results are rounded for display; calculations use unrounded values. Read our calculation methodology.
Understanding the result
Current is voltage divided by resistance. Power is the resulting rate of electrical energy transfer in the ideal resistor.
When this tool is useful
Check a simple DC resistive circuit using consistent volts and ohms.
Understanding your inputs
| Input | What to enter |
|---|---|
| Voltage (V) | Enter a number of at least 0 and no more than 1000000000. |
| Resistance (Ω) | Enter a number of at least 0.000001 and no more than 1000000000000. |
Frequently asked questions
Does this model every electrical component?
No. It assumes an ohmic resistor. Nonlinear devices and AC impedance can require different models.
Is the computed power a safe resistor rating?
It is the theoretical dissipation. Selecting components also requires thermal derating and the manufacturer’s limits.