Resistor Series/Parallel Network Calculator

Resistors in series add directly — the same current flows through each, so their voltage drops (and therefore resistances) add: R_eq = R1 + R2 + ... + Rn. Resistors in parallel share the same voltage across each, so their conductances (1/R) add instead: 1/R_eq = 1/R1 + 1/R2 + ... + 1/Rn. This calculator applies whichever rule matches the topology you select across up to six resistors and shows the summed terms.

Use it to reduce a simple resistor network to a single equivalent value — checking a voltage-divider design, verifying a parallel combination used to hit a non-standard resistance value, or working a circuits-course problem. For a genuine series-parallel or bridge network, reduce the circuit by hand into series and parallel sub-groups first, then use this calculator on each group in turn.

This calculator computes purely resistive combinations at DC or at a frequency where reactance is negligible — it does not handle impedance (resistors combined with capacitors or inductors) or networks that aren't reducible to simple series/parallel groups, such as a Wheatstone bridge away from balance, which requires mesh or nodal analysis instead.