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Total resistance for any list of resistors in series or parallel.
Resistor Calculator (Series & Parallel) is loading — interactive editor will appear here. Use examples below to try instantly once loaded.
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Computes the equivalent resistance of a list of resistors wired in series (sum) or in parallel (reciprocal sum).
Network resistance math is trivial for two equal resistors but error-prone with mixed values: the reciprocal sum needs to be done carefully, and the answer must always be below the smallest resistor for parallel networks. This tool shows both, so you can sanity-check your own work.
This tool is part of the DevStackIO platform — a collection of free online developer tools from DevStackIO. Browse more free developer resources on DevStackIO.
Electronics hobbyists, EE students, circuit designers, and anyone analyzing or building resistor networks.
Enter resistances in ohms, separated by commas or spaces
The panel shows both the series total and the parallel total
Compare the parallel result to the smallest resistor — it must always be lower
10, 10 → series 20 Ω, parallel 5 Ω4, 12 → parallel 3 Ω100, 100, 100 → series 300 Ω, parallel ≈ 33.33 Ω10, 20, 5 → series 35 Ω, parallel ≈ 2.857 ΩQ: Can I mix units? A: No
use all ohms or all kilohms consistently; the tool treats numbers literally.
Q: What about capacitors or inductors?
A: The same formulas apply with different directions (capacitors sum in parallel, reciprocal in series).
Q: Why is parallel so counterintuitive? A: Each added resistor opens a new current path
the total conductance grows, so resistance falls.
Q: Number of resistors?
A: Any list of two or more.
Authoritative specifications, standards, and in-depth reading for Resistor Calculator (Series & Parallel).
Series (Σ)
35 Ω
10 + 20 + 5
Parallel (1/Σ 1/R)
2.8571 Ω
Parallel total always below the smallest resistor
Series: R = R₁ + R₂ + … Parallel: 1/R = 1/R₁ + 1/R₂ + … Runs locally.
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