Ω Ohm's Law Calculator for Electrical
Calculate resistance and power from voltage and current.
This free tool helps you turn project measurements into a practical planning estimate. Enter values in Vaelden’s interactive calculator, review the result, and confirm important assumptions against supplier data, measurements, codes or qualified advice before committing materials or money.
Open the Ohm's Law calculator →
How to calculate ohm's law
Method: Resistance = voltage ÷ current; power = voltage × current
- Use voltage across the component.
- Use current through the same component under steady conditions.
- Calculate resistance and power, then compare with component ratings.
Worked example
Using these planning inputs:
- Voltage: 12 V
- Current: 2 A
Resistance: 6.000 Ω
Reality check: This simple relationship suits DC and resistive loads; reactive AC circuits, transients and non-linear devices need additional analysis.
Method status and references
Dimensional equation. The result applies to steady-state DC or resistive behaviour; reactive and nonlinear AC loads need additional modelling.
Before you calculate
Use consistent units and the best measured inputs available. Real materials, equipment, site conditions and tolerances can change the result. Vaelden shows planning estimates; regulated, structural, electrical, plumbing, pressure and other safety-critical work still requires appropriate local compliance and professional advice.