Resistors in Series and Parallel Calculator
Combine up to four resistors. Leave unused values at 0.
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Series total (Ω)
Series total (Ω)
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Parallel total (Ω)
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Resistors in Series and Parallel Calculator by TheCalcTools
How the Resistors in Series and Parallel Calculator works
Enter the values of the resistors in ohms. Use 0 for resistors you are not using.
In series, resistances add.
In parallel, the reciprocals add, so the total is always smaller than the smallest resistor.
The formula
Series: R = R₁ + R₂ + R₃ + …Parallel: 1 ÷ R = 1 ÷ R₁ + 1 ÷ R₂ + 1 ÷ R₃ + …
Worked example
Using the default values shown in the calculator:
| R1 (Ω) | 100 |
|---|---|
| R2 (Ω) | 220 |
| R3 (Ω) | 330 |
| R4 (Ω, 0 = unused) | 0 |
- Series: 100 + 220 + 330 = 650 Ω.
- Parallel: 1 ÷ (1/100 + 1/220 + 1/330) = 56.897 Ω.
Result:
| Series total (Ω) | 650.000 |
|---|---|
| Parallel total (Ω) | 56.897 |
Frequently asked questions
Why is the parallel total smaller than each resistor?
Each added path gives current another route, so the combination conducts more than any single resistor.
What about two resistors in parallel?
A shortcut is R = R₁R₂ ÷ (R₁ + R₂), the product over the sum.
Sources and further reading
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This calculator gives estimates for information only. Check important results independently before you rely on them. See our disclaimer.