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Parallel and Series Resistance Calculator & Solver

Calculate equivalent resistance for series and parallel circuits. Includes a 'Target Resistor Solver' to find component combinations for specific values.

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Category Electronics
Ω
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Result: -- Ω
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About

Designing simplified circuits often requires achieving a specific resistance value that doesn't exist in standard manufacturing series (E12/E24). This tool serves two purposes: determining the total equivalent resistance (Req) of a complex network, and solving the reverse problem—suggesting combinations of standard resistors to approximate a target value.

It applies Kirchhoff's circuit laws dynamically. In Series, resistance adds up linearly. In Parallel, the reciprocal of the total resistance is the sum of the reciprocals of individual resistances, reducing the total impedance below the smallest component value.

circuit resistance series parallel electronics solver

Formulas

For two resistors in parallel, the 'product over sum' rule is often used for quick calculation:

Req = R1 × R2R1 + R2

Reference Data

ConfigurationFormulaBehavior
SeriesRtotal = R1 + R2 ...Increases Resistance
Parallel1Rtotal = 1R1 + 1R2 ...Decreases Resistance

Frequently Asked Questions

Parallel resistors are used to achieve non-standard values or to distribute power (heat) dissipation. Two 0.5W resistors in parallel can handle 1W total power.
Yes. This is called a Series-Parallel combination. You solve it by simplifying the circuit in steps: calculate the equivalent of the parallel sections first, then add them to the series components.