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Resistor Series/Parallel Calculator

Find the total resistance of two resistors in series or parallel.

Inputs

Saved Scenarios

— select 2+ to compare

Total Resistance (Ω)

320.00

Spark says

How it's calculated

Formula

Series:RT=R1+R2Parallel:RT=R1R2R1+R2Series: R_T = R_1 + R_2 \quad\quad Parallel: R_T = \dfrac{R_1 R_2}{R_1 + R_2}
R_1, R_2
— The two resistor values

What is the Resistor Series/Parallel Calculator?

Resistors combine differently depending on configuration: in series their resistances add directly; in parallel, the combined resistance is always lower than either individual resistor.

How to use it

  1. 1 Enter both resistor values.
  2. 2 Choose series or parallel configuration.

Worked examples

100Ω and 220Ω in parallel

Total resistance is about 68.75Ω.

Try it

Frequently asked questions

Why is parallel resistance always lower than either resistor?

Parallel paths give current more routes to flow, effectively increasing the cross-sectional area for current — which always reduces total resistance below the smallest individual value.