What this calculator does
Resistors in series & parallel works out combined resistance of up to four resistors. Enter your own figures above and the answer updates as you type: nothing is fixed in the code, so the result reflects exactly the numbers you supply.
The formula this calculator evaluates is printed under the tool and explained below, so you can check the working by hand or reuse it in a spreadsheet.
The formula
FormulaSeries: R = R₁+R₂+… · Parallel: 1/R = 1/R₁ + 1/R₂ + …
The inputs explained
| Field | What to enter |
|---|---|
| R₁ (Ω) | A number, measured in Ω. Starts at 100. |
| R₂ (Ω) | A number, measured in Ω. Starts at 220. |
| R₃ (0 to ignore) (Ω) | A number, measured in Ω. Starts at 0. |
| R₄ (0 to ignore) (Ω) | A number, measured in Ω. Starts at 0. |
Worked examples
Every figure in the tables below is produced by this page’s own calculator at build time, so the numbers and the tool always agree. Select any row to load that scenario.
How the answer changes with r₁
Every other input is held at the calculator’s starting values while r₁ varies. Select any row to load that scenario into the calculator.