Series & Parallel Resistance Calculator
Find the total resistance of resistors wired in series or in parallel, with the equivalent value updated as you add components. Calculates in your browser.
Total
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Show the math
Resistors add in series and combine reciprocally in parallel; capacitors do the opposite:
series R = R₁ + R₂ + …
parallel R = 1 ÷ (1/R₁ + 1/R₂ + …)
Capacitors follow the mirror-image rule, they add in parallel and combine reciprocally in series. All math runs in your browser.
What this does
A series & parallel resistance calculator finds the total resistance of resistors wired in series or in parallel, updating as you add components.
How to use it
- Choose series or parallel.
- Add each resistor value.
- Read the equivalent resistance.
- Add or remove components freely.
How it works
In series resistances add; in parallel the reciprocals add, so the total is always smaller than the smallest resistor.
series: R = R₁ + R₂ …; parallel: 1/R = 1/R₁ + 1/R₂ …
Understanding your result
The useful sanity check is direction: series resistance always adds up to more than any single resistor, while parallel resistance is always smaller than the smallest one. If your total comes out the wrong side of that, you have mixed up the wiring. Parallel paths also share current, so each branch carries less than the whole.
Example
Two 100 Ω resistors give 200 Ω in series or 50 Ω in parallel.
Sources & methodology
Last updated .
Frequently asked questions
How do series resistors add up?
In series the resistances simply add: R = R₁ + R₂ + R₃ … The current is the same through each part.
How do parallel resistors combine?
In parallel the reciprocals add: 1/R = 1/R₁ + 1/R₂ … so the total is always smaller than the smallest resistor.
Is my data stored?
No. Everything is calculated locally in your browser.
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