Resistors in series and parallel calculator
Calculate the equivalent resistance of resistors in series or parallel, and of capacitors too, by typing the values separated by commas or lines.
Equivalent resistance: series and parallel
Everything happens on your device: nothing is uploaded to the internet.
Available in: 
Resistors in series and parallel calculator: what it is for
Type the values separated by semicolons or lines, using prefixes like k, M, µ and n. The tool calculates both the series and the parallel connection for resistors or capacitors at the same time.
How to use
- Choose resistors or capacitors.
- Type the values.
- See the series and parallel equivalents.
When to use it
- Solve physics exercises.
- Get a value you don't have in the drawer.
- Design filters and dividers.
Frequently asked questions
How do I calculate resistors in series?
Add the values: 100 Ω + 220 Ω + 330 Ω = 650 Ω. The current is the same through all of them and the equivalent resistance is always larger than the largest one.
And in parallel?
The inverse of the equivalent is the sum of the inverses: 1/Req = 1/R1 + 1/R2 + ... For two resistors, Req = (R1 × R2) ÷ (R1 + R2). The result is always smaller than the smallest resistor.
What about capacitors?
It is the opposite of resistors: in parallel capacitances add up and in series the inverse rule applies.
Is it really free?
Yes, 100% free. No sign-up, no subscription and no usage limits. All Tools123 tools are free and run right in your browser.