Using the Resistor Calculator
Enter every resistance in ohms. In series, resistances add; in parallel, their reciprocals add and the reciprocal of that sum gives the equivalent. All entries must be positive, and the selected connection applies to the entire list.
Worked example
Use the example inputs below to reproduce this result. These are the form's starting values, not recommended targets. Changing your inputs updates your result above; this worked example stays fixed for comparison. Results are rounded for display.
Example inputs
- Resistances (Ω)
- 100, 200, 300
- Connection
- Series
Example result
- Equivalent resistance (Ω)
- 600
Method and assumptions
Series resistances add; parallel reciprocals add.
Distinguish a model from a circuit specification
Electrical calculations describe the assumptions entered in the form. Real components, cables and supplies also have ratings, tolerances and operating conditions. Confirm whether the model is for DC resistance, energy over time or another specific quantity. A mathematically consistent result is not by itself a complete design or installation check.
Common question
Why is parallel resistance smaller than an individual branch resistance?
Parallel branches provide additional paths for current. With positive resistor values, their conductances add, so the equivalent resistance is below the smallest branch value when there is more than one branch. Series connections instead add resistance.
Guide updated .