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Electrical

Ohm's Law Calculator

Ohm's law relates voltage (V), current (I), and resistance (R) in a purely resistive or DC circuit. Given any two of the three quantities, this calculator solves for the third. It does not include AC impedance, reactance, or cable sizing.

TypeInteractive calculator — separate from unit conversions

Calculator

Result
Voltage20 V

Formulas

Voltage
V = I × R
Current
I = V / R
Resistance
R = V / I

Diagram

Ohm's Law: V = I × R+−VRIV = I × R

Worked example

A resistor of 10 Ω carries a current of 2 A. What is the voltage across it?

  1. 01V = I × R
  2. 02V = 2 × 10
  3. 03V = 20 V
Result

The voltage across the 10 Ω resistor at 2 A is 20 V.

FAQ

Does this calculator handle AC circuits?
No. This is for DC or purely resistive circuits only. For AC circuits with inductive or capacitive loads, you would need impedance (Z), which combines resistance and reactance. Ohm's law in its simple form (V = IR) applies only to the resistive component.
Is this a cable sizing calculator?
No. This calculator does not select conductor sizes, apply derating factors, or reference any electrical code. It calculates the basic V/I/R relationship only.
Does this include temperature effects on resistance?
No. Resistance is treated as a fixed input. Temperature coefficients of resistance are not implemented.
Can I use this for three-phase circuits?
No. This calculator is for a single-load DC/resistive basis. Three-phase power calculations require additional factors (line vs phase, power factor) that are outside scope.