∥ Parallel Resistors Calculator for Electrical
Calculate equivalent resistance and total current for three branches.
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 Parallel Resistors calculator →
How to calculate parallel resistors
Method: Equivalent resistance = 1 ÷ (1/R1 + 1/R2 + 1/R3)
- Use only branches connected across the same two nodes.
- Add reciprocal resistances and invert the sum.
- Calculate branch current and individual power at the applied voltage.
Worked example
Using these planning inputs:
- Resistance 1: 100 Ω
- Resistance 2: 220 Ω
- Resistance 3: 330 Ω
- Applied voltage: 12 V
Equivalent resistance: 56.897 Ω
Reality check: Confirm branch and source current ratings; a failed or disconnected branch changes the equivalent circuit.
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.