Series & parallel resistor calculator
Add up to ten resistor values and see the total resistance when they are connected in series and in parallel. Handy for building a value you don't have from the parts in your drawer.
Enter your values
Add up to 10 resistors. See the total if they are joined end to end (series) or side by side (parallel).
Result
Series: R = R1 + R2 + …Parallel: 1/R = 1/R1 + 1/R2 + …Two in parallel: R1×R2 ÷ (R1+R2)Coro's tip: Two equal resistors in parallel give half the value. Two 1 kΩ in parallel make 500 Ω. That trick helps when you don't have the exact value.
Series & parallel resistor calculator: common questions
How do you calculate resistors in series?
Add them: R = R1 + R2 + R3 + …
How do you calculate resistors in parallel?
Add the reciprocals and invert: 1/R = 1/R1 + 1/R2 + … For two resistors, R = R1 × R2 ÷ (R1 + R2).
What do two equal resistors in parallel give?
Half the value. Two 1 kΩ resistors in parallel give 500 Ω.
For learning and low-voltage hobby circuits (12 V and below). Always check the part's datasheet. Never use these tools to plan mains (230 V) wiring.