Ohm’s Law Calculator
Enter two electrical quantities to find voltage, current, resistance and power for an ideal DC resistor. Follow the equations and current–voltage graph.
YOUR CALCULATION
Result
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Calculation steps
Work through one step at a time or reveal the complete calculation. The steps use your current inputs.
How to calculate
An ideal ohmic resistor follows V = IR. Electrical power is P = VI, equivalently I²R or V²/R. Substitute the two known quantities to solve the other two. The line graph keeps the solved resistance constant.
V = IR; P = VI = I²R = V²/R
Worked example
At 12 V across a 6 Ω ideal resistor, I = 12/6 = 2 A and P = 12 × 2 = 24 W. Doubling voltage across the same resistance doubles current and quadruples power.
Assumptions and input details
This is an ideal DC resistor model, not an AC impedance or component-rating calculator. Non-negative zero voltage/current is allowed when a positive resistance is supplied. Pairs that do not uniquely determine a finite resistance require positive inputs.
References: OpenStax: Ohm’s law
Unit definitions
Unit selection is independent of language. Each selector contains only units for its physical quantity. Calculations use defined base units internally.
SI prefixes are explicit: for example, milli means one thousandth, micro one millionth and kilo one thousand. Changing a unit changes the interpretation of the entered number.
Using this calculator
Can I enter my own problem?
Yes. Replace the example values with your own inputs. The result, calculation steps, tables and applicable diagrams update from those inputs. Blank or invalid values clear the result; example values are never silently substituted for missing inputs.
Are the results exact?
Results use floating-point arithmetic and displayed rounding. Read the formula, assumptions and any stated data precision before interpreting the result.
Is my input uploaded?
The calculation runs in your browser. No account, file upload or external AI service is required. Inputs are not saved between page reloads.
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