Add your resistors and you'll see the total resistance in series and in parallel side by side, as you type. Values like 4k7 and 1M work.
Don't have the exact value? Type the value you need and the calculator finds pairs of standard resistors, in series or in parallel, that get closest.
How to use
- Type the value of each resistor; Add resistor adds more.
- Read the totals: series and parallel are shown side by side.
- Under Find standard resistors for a value, type the value you need and pick the series you have in your drawer (E12 is the usual starter kit).
- The list shows the best combinations and the error of each.
Resistors in series
In series, resistances add up: 100 + 220 + 330 = 650 Ω. The same current flows through all of them, and the voltage splits in proportion to each value.
Resistors in parallel
In parallel, the total is always lower than the smallest resistor: 1 ÷ (1/R1 + 1/R2 + …). Two equal resistors give half: two 1 kΩ resistors make 500 Ω. Each resistor carries part of the current, which also spreads the heat.