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Electronics resistance tool
Series/Parallel Resistor Calculator
Enter two to four resistor values and switch between series and parallel layouts to calculate equivalent resistance instantly.
Did you know? Series resistors share one current path, while parallel resistors create multiple current paths. That is why series totals rise and parallel totals drop.
Resistor values
Enter at least R1 and R2. R3 and R4 are optional.
Equivalent resistance—ohm
ModeSeries
Included0 resistors
OutputReq
Enter at least two resistor values to begin.
Live circuit visualization
The circuit redraws for series or parallel mode and animates only for valid values.
Equivalent resistance result—ohm
Series
ViewSeries chain
Active0 active resistors
StatusEnter two resistor values.
In parallel mode, lower-resistance branches animate faster and brighter because they carry more of the current.
How the result is calculated
Choose a mode and enter at least two resistor values. The calculator will show the selected formula and substitution steps.
Req = R1 + R2 + …
1Choose series or parallel mode.
2Enter at least two resistor values in ohms.
3Review the equivalent resistance and live circuit view.