What is the Series & Parallel Resistor Calculator?
Calculate total resistance of resistors in series and in parallel. Combining resistors in series or parallel changes the total resistance, which lets you build values that are not available off the shelf.
How to use the Series & Parallel Resistor Calculator
- Enter your resistor values.
- Results update automatically as you type; you can also press Calculate.
- Read the output: series total, parallel total.
- Use the 📊 chart to see the result visually, then copy or share it.
Formula and method
Worked example
With resistor values = 100, 220, 330, the Series & Parallel Resistor Calculator returns series total: 650 Ω; parallel total: 56.8965517241 Ω.
Where the Series & Parallel Resistor Calculator helps in real life
A hobbyist needs about 150 Ω but only has 100 Ω and 47 Ω resistors. Combining them in series gives 147 Ω, close enough for most circuits.
A student wants to check the total resistance of three resistors wired in parallel before measuring it on a breadboard.
Common mistakes to avoid
- Adding parallel resistors directly instead of using reciprocals.
- Mixing ohms and kilohms in the same calculation.
- Ignoring each resistor’s tolerance band.
- Forgetting that every resistor in series carries the same current.
💡 Practical tip: The total of resistors in parallel is always smaller than the smallest individual resistor.
Tips for better results
- Use reciprocals for parallel combinations.
- Convert all values to the same unit first.
- Measure the finished combination with a multimeter.
Frequently asked questions
What does the Series & Parallel Resistor Calculator do?
Calculate total resistance of resistors in series and in parallel.
How is it calculated?
The Series & Parallel Resistor Calculator uses this method: Series: R = R₁ + R₂ + …; Parallel: 1/R = 1/R₁ + 1/R₂ + ….
Can you show an example?
With resistor values = 100, 220, 330, the Series & Parallel Resistor Calculator returns series total: 650 Ω; parallel total: 56.8965517241 Ω.
Is the Series & Parallel Resistor Calculator accurate?
Yes. It uses standard formulas and exact constants, and the results are verified by our automated test suite. Values are displayed to up to 12 significant digits.
Is this tool free and private?
Yes — the Series & Parallel Resistor Calculator is completely free with no sign-up, and it runs entirely in your browser, so the values you enter are never uploaded to our servers.
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