Series and Parallel Resistor Calculator

Add the values together. Resistors in series carry the same current, so the total resistance is R1 + R2 + ... + Rn. Three resistors of 100, 200 and 300 ohm in series give 600 ohm.

Take the reciprocal of the sum of reciprocals: 1 / R_total = 1/R1 + 1/R2 + ... The combined value is always smaller than the smallest resistor in the group. For 60 and 40 ohm that is 1 / (1/60 + 1/40) = 24 ohm.

Exactly half of one of them. Two 100 ohm resistors in parallel give 50 ohm, since 1 / (1/100 + 1/100) = 50. More generally, n equal resistors in parallel give one value divided by n.

Type them into the Resistance values box separated by new lines, spaces or commas. The calculator splits on any of those, so a mix like '100, 200 300' works too. Each entry is read as a number in ohms.

Yes. You can enter decimal values like 4.7 and large values like 10000 for a 10k resistor. Enter the plain ohm value; the tool does not parse suffixes such as k or M.

The result is rounded to nine decimal places to hide floating-point noise, so clean cases like 24 or 600 show as whole numbers while awkward parallel combinations keep useful precision.

Not in one pass. Solve each group on its own first: combine a parallel block into a single value here, then switch to series and add that value with the rest. Repeat for more complex networks.

A zero-ohm entry is a short circuit and a negative resistance is not physical, so both are rejected. This also keeps the parallel formula well defined, since dividing by zero has no meaning.

No. The calculation runs entirely in your browser using a simple arithmetic formula, so nothing you enter leaves your device.