Resistors in series and parallel

Total resistance for any list of resistors, in series or in parallel.

Calculating…

How it's calculated

Series: R = R1 + R2 + R3 … Parallel: 1/R = 1/R1 + 1/R2 + 1/R3 …

In series, resistances add. In parallel, the total is always lower than the smallest resistor. Two equal resistors in parallel give half the value of one.

A common use is working out a replacement for an obsolete resistor from values you have in stock.