Technical utilities
Ohm's Law Calculator
Ohm's law states that voltage equals current multiplied by resistance. Power equals voltage multiplied by current and can be rearranged with any valid pair of known values.
Solve voltage, current, resistance, and power from any sufficient pair of electrical values.
Calculated result
Solved electrical values
Calculating…
Calculated locally in your browser
Planning math only. Verify equipment specifications and installation requirements separately.
What this calculator returns
Enter two independent values. If more than two values are entered, they must agree within the displayed tolerance.
Formula and variables
The calculation runs entirely in your browser. Static formulas, definitions, examples, and tables remain readable without JavaScript.
V = I × R; P = V × I = I²R = V²/R.
- V
- Voltage across the modeled component or network.
- I
- Current through the modeled component or network.
- R
- Resistance in ohms; subscripts identify individual resistors.
- P
- Power dissipated or delivered, in watts.
V is voltage, I is current, R is resistance, and P is power.
Worked example
| Input | Value |
|---|---|
| Voltage | 12 V |
| Current | A |
| Resistance | 6 Ω |
| Power | W |
With 12 V across 6 Ω, current is 2 A and power is 24 W.
Reference table
| Solve for | Formula variants |
|---|---|
| Voltage | V = I × R; V = P / I; V = √(P × R) |
| Current | I = V / R; I = P / V; I = √(P / R) |
| Resistance | R = V / I; R = V² / P; R = P / I² |
| Power | P = V × I; P = I² × R; P = V² / R |
| Networks | Series: Req = ΣR; parallel: 1/Req = Σ(1/R) |
Frequently asked questions
Can Ohm's law calculate power too?
Yes. Once two independent electrical values are known, the tool derives voltage, current, resistance, and power from the related equations.
Why are conflicting entered values rejected?
More than two entered values overdetermine the relationship, so the tool checks that they agree within its displayed tolerance.
Which two values can I enter?
Any valid independent pair among voltage, current, resistance, and power.
Assumptions and limitations
- Pure steady-state math.
- Does not model reactive components, transients, or thermal limits.
Method and sources
Review the electrical formulas, calculation methodology, and reference tables for the references most relevant to this calculation. The broader technical sources index records source scope and verification. Last reviewed .