Electronics CalculatorsSeries and parallel resistor calculator
Type two or more resistor values separated by spaces or commas.
The rules
- Series: R = R1 + R2 + R3 ... The same current flows through all of them.
- Parallel: 1 / R = 1 / R1 + 1 / R2 + 1 / R3 ... The same voltage is across all of them. The total is always smaller than the smallest resistor.
Making a value you do not have
Two equal resistors in parallel give half the value, and in series twice the value. For example two 100 Ω in parallel make 50 Ω. To make a value that is not in the E-series, combine two resistors in series or parallel and check the result here.
How it was tested
We compared the results with direct calculation for sets of values. Examples: 100 and 100 in parallel give 50 Ω, and 1 k, 2 k and 3 k in parallel give 545.5 Ω.
Is there a formula for two in parallel?
Yes: R1 × R2 / (R1 + R2).
Does the total power add up?
The total power is the sum of what each resistor dissipates.
This is an independent guide. It is not connected with any standards body or company named here. The formulas are the usual textbook ones; the colour code, E-series and AWG values are those printed in common references, because the standards IEC 60062, IEC 60063 and ASTM B258 are paid documents that we did not read. Tables and examples were calculated with Python on 14 November 2026. Check data sheets and local safety rules before you build.