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Resistors in Series and Parallel Calculator

Find the equivalent resistance of up to three resistors wired in series or in parallel.

Equivalent resistance
320 Ω
Resistors used (nonzero values)
2

How it works

Resistors wired in series share the same current, so their resistances simply add: R_total = R1 + R2 + R3. Resistors wired in parallel share the same voltage across each branch instead, so their conductances (1/R) add: 1/R_total = 1/R1 + 1/R2 + 1/R3, which always makes the parallel total smaller than the smallest individual resistor.

Leaving Resistor 3 at 0 treats it as not present — in series that adds nothing to the sum automatically, and in parallel it's explicitly skipped rather than treated as a literal 0-ohm short circuit, so the same three-field form works for either a two- or three-resistor combination.

FAQ

Why is the parallel total always smaller than any single resistor?

Adding a parallel branch gives current another path to flow through, which can only make it easier (never harder) for current to get through overall — so the combined resistance always drops below whichever individual resistor is smallest.

How is this different from the resistor color code calculator?

That calculator decodes a single physical resistor's painted color bands into its resistance value. This one takes resistance values you already know (from a datasheet, a multimeter, or that calculator) and combines several of them into one equivalent value for a series or parallel circuit.

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