Add up resistors in series, or combine them in parallel. Enter any number of values and get both totals at once.
Series resistance is simply the sum. Parallel resistance uses 1/Rtotal = 1/R1 + 1/R2 + … and is always smaller than the smallest resistor. Two equal resistors in parallel give half their value.
In series, total resistance is just the sum of all values. In parallel, you add the reciprocals and invert: 1/Rtotal = 1/R1 + 1/R2 + … This tool computes both from your list at once.
Adding a parallel path gives the current another route, which lowers overall resistance. The result is always less than the smallest resistor in the group; two equal resistors in parallel give exactly half.
This tool handles a single group at a time. For a mixed network, reduce it step by step: combine each parallel cluster into one value, then add the series sections.