➕ Series Resistors Calculator for Electrical
Calculate total resistance and current for three resistors in series.
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 Series Resistors calculator →
How to calculate series resistors
Method: Series resistance = R1 + R2 + R3; circuit current = voltage ÷ total resistance
- Add every series resistance.
- Divide supply voltage by the total.
- Calculate each resistor’s voltage drop and power before choosing ratings.
Worked example
Using these planning inputs:
- Resistance 1: 100 Ω
- Resistance 2: 220 Ω
- Resistance 3: 330 Ω
- Applied voltage: 12 V
Total resistance: 650.000 Ω
Reality check: Check resistor tolerance, temperature coefficient and power derating; ideal arithmetic does not protect components from transients.
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.