When to use this calculator
Find equivalent resistance for two positive resistors in parallel. Parallel branches share the same voltage.
Explore the dc circuits & components calculators for other questions in this topic. For a related calculation, use the RC Time Constant Calculator: Calculate a resistor-capacitor circuit’s time constant.
PUTTING IT INTO PRACTICE
Parallel Resistance: a worked example
The values below are an illustrative example, not a recommendation. Replace them with measurements or assumptions that match your question.
| Input | Example value |
|---|---|
| First resistance (Ω) | 10 |
| Second resistance (Ω) | 20 |
| Result | 6.666667 Ω |
- Check the input labels and enter the example values above.
- Apply the relationship: Equivalent resistance = R₁R₂ ÷ (R₁ + R₂).
- The result is 6.666667 Ω, rounded for display.
How to interpret your result
Parallel branches share the same voltage.
Ideal component models omit tolerances, heat and parasitic effects. Distinguish nominal energy from usable energy for batteries. Component ratings and installation requirements need separate manufacturer and design checks.
Frequently asked questions
Can these calculations select a safe installation rating?
No. They explain ideal relationships and do not include every thermal, protective or regulatory requirement.
How do I use the parallel resistance calculator?
Enter first resistance (ω), second resistance (ω). The result updates automatically. Use the units shown beside each input; the example values illustrate the method.
Which formula does this calculator use?
Equivalent resistance = R₁R₂ ÷ (R₁ + R₂).
What should I check before using the result?
Parallel branches share the same voltage.
How are results rounded?
Scalar numbers display up to six decimal places, with scientific notation for very large or small values. Text, fraction, date and schedule outputs use the format described on the tool. Intermediate calculations use JavaScript floating-point arithmetic. Keep sensible precision for your measurements.
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