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Series and parallel resistors calculator
Calculate equivalent resistance for two resistors in series and parallel.
On this page
Series resistance320Ω
Parallel resistance68.75Ω
Calculator controls
How to calculate
Calculate equivalent resistance for two resistors in series and parallel.
Series resistance = r1+r2; Parallel resistance = r1*r2/(r1+r2)
Worked example
Example inputs
Resistance 1: 100 · Resistance 2: 220
Example resultSeries resistance: 320 Ω · Parallel resistance: 68.75 Ω
Assumptions and limits
These ideal formulas ignore component tolerance, temperature and frequency effects. De-energize circuits before measurement.
Results are rounded for display; calculations use unrounded values. Read our calculation methodology.
Understanding the result
Calculate equivalent resistance for two resistors in series and parallel. The displayed figures use the inputs and formula shown on this page.
When this tool is useful
Use the series and parallel resistors to compare a scenario, check an estimate, or verify a manual calculation.
Understanding your inputs
| Input | What to enter |
|---|---|
| Resistance 1 | Enter a number of at least 0.000001 and no more than 1000000000000. |
| Resistance 2 | Enter a number of at least 0.000001 and no more than 1000000000000. |
Frequently asked questions
What should I check before using the series and parallel resistors result?
These ideal formulas ignore component tolerance, temperature and frequency effects. De-energize circuits before measurement.
Is this series and parallel resistors result exact?
It is exact for the stated mathematical model and entered values. Real-world results can differ when rates, timing, fees, definitions or measurement conditions differ.