Electric Circuit Calculator
Enter the resistor values and choose series or parallel.
This result is an estimate only. Double-check important figures before relying on them.
How it is calculated
- Series: R total = R₁ + R₂ + …
- Parallel: R total = 1 ÷ (1 ÷ R₁ + 1 ÷ R₂ + …)
- Current = V ÷ R total, power = V × current
For one resistor, use the Ohm’s law calculator. For capacitors, see the capacitance calculator.
Worked example
100, 200 and 300 Ω in series on 12 V:
- Total = 600 Ω
- Current = 0.02 A and power = 0.24 W
Why your number may differ
Resistors have tolerances, often 1% to 5%, and their value shifts with temperature. Check the power rating of each resistor.
Frequently asked questions
How do resistors add in series?
Simply add them: R total = R₁ + R₂ + R₃. The same current flows through each.
How do they combine in parallel?
1 ÷ R total = 1 ÷ R₁ + 1 ÷ R₂ + 1 ÷ R₃. The total is lower than the smallest resistor.
How are current and power found?
With a supply voltage, current = V ÷ R total and power = V × current.