Series and Parallel Resistance Calculator
Calculate the total resistance of resistors in series and in parallel from a list of resistance values in ohms.
Last reviewed by the Radiatus Cloud team
Calculate the total resistance of resistors in series and in parallel.
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Calculate series and parallel resistance
Resistors can be combined in two basic ways, and this calculator finds the total resistance for both from a list of values. In series, where resistors are connected end to end so the same current flows through each, the total resistance is simply the sum of the individual resistances. In parallel, where resistors share the same two connection points so the current divides among them, the reciprocal of the total equals the sum of the reciprocals, which always yields a total smaller than the smallest resistor.
Enter any number of resistor values and the calculator computes both totals at once.
Combining resistors
Understanding series and parallel combinations is essential for circuit design and analysis. Adding resistors in series increases resistance and divides voltage, while adding them in parallel decreases resistance and divides current. Real circuits often mix the two, and complex networks are solved by repeatedly reducing series and parallel groups to a single equivalent resistance.
A useful check is that the parallel total is always less than the smallest resistor in the group, since adding a parallel path always provides more ways for current to flow. All calculation happens locally in your browser.
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Frequently Asked Questions
How do I add resistors in series?
Simply add the resistance values together. In series the same current flows through each resistor, so their resistances sum.
How do I add resistors in parallel?
Add the reciprocals of the resistances and take the reciprocal of the sum. The parallel total is always less than the smallest resistor.
Why is parallel resistance always smaller?
Each parallel path gives current another route, so adding resistors in parallel increases the total current and lowers the equivalent resistance.
Can I mix series and parallel?
Real circuits often do. Reduce series and parallel groups step by step to a single equivalent resistance to analyse them.
What happens to voltage and current?
Series resistors divide the voltage and share the current, while parallel resistors share the voltage and divide the current.
Privacy & Security
Everything runs in your browser; nothing is uploaded.
How to Use
Enter resistor values separated by commas or new lines.
Disclaimer: This tool is provided "as is" without warranty of any kind. Results are for educational and utility purposes.