Parallel Resistor Calculator
Combine two or more positive resistance values using reciprocal conductance. An entered source voltage is then applied to the equivalent resistance for ideal total current and power.
How to use the Parallel Resistor Calculator
Enter two or more resistance values in ohms and an applied source voltage.
Review component tolerance, temperature coefficient, power ratings, source limits, and whether the actual network is purely parallel.
Read equivalent resistance, branch count, total current, and total ideal power.
Formula
Equivalent resistance Rₑq = 1 ÷ Σ(1 ÷ Rᵢ). Total current = source voltage ÷ Rₑq, and total ideal power = source voltage² ÷ Rₑq.
Example
A 100 Ω resistor in parallel with 200 Ω gives Rₑq = 100 × 200 ÷ 300 = 66.667 Ω.
Assumptions and limitations
- The model uses ideal resistors and does not verify tolerance, component ratings, temperature, fault current, wiring, or safe isolation; de-energize hazardous circuits and seek qualified review.
- Parallel Resistor Calculator treats the entered values as estimates and does not infer missing project, account, or personal details.
- Calculations retain working precision except where the cited method requires an intermediate rounding step; displayed values are then formatted separately. Source rules and dated rates must be rechecked when they change.
Sources
- All About Circuits: Resistors in ParallelParallel-circuit resistance and current relationships. Reviewed 2026-08-14.
- National Institute of Standards and Technology: SI Units — Electric CurrentSI electrical units and definitions. Reviewed 2026-08-14.
- OpenStax: University Physics Volume 2 — Resistors in Series and ParallelOfficial formula, rate, or program guidance used by this calculator. Reviewed 2026-08-14.
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Frequently asked questions
How does the Parallel Resistor Calculator work?
Equivalent resistance Rₑq = 1 ÷ Σ(1 ÷ Rᵢ). Total current = source voltage ÷ Rₑq, and total ideal power = source voltage² ÷ Rₑq.
What information should I enter in the Parallel Resistor Calculator?
Enter two or more resistance values in ohms and an applied source voltage, then verify component tolerance, temperature coefficient, power ratings, source limits, and whether the actual network is purely parallel.
What should I verify before using this Parallel Resistor Calculator result?
The model uses ideal resistors and does not verify tolerance, component ratings, temperature, fault current, wiring, or safe isolation; de-energize hazardous circuits and seek qualified review.
Reviewed 2026-08-14 · 1.0.0 · content-2026-08-14 · Trusty Calculator Editorial Team