Parallel Resistance
Use the Parallel Resistance. Enter Resistance 1 (Ω) and Resistance 2 (Ω) for a clear result, formula explanation, and practical planning checks.
Parallel Resistance measurements
Enter your values, then calculate.
Result
How to calculate parallel resistance
This calculator finds the combined resistance of up to three resistors wired in parallel — a fundamental electrical circuit calculation.
How the calculation works
Combined resistance = 1 ÷ (1/R1 + 1/R2 + 1/R3). The reciprocal of combined resistance equals the sum of the reciprocals of each individual resistance.
Example
Three resistors of 100Ω, 200Ω, and 300Ω in parallel: 1 ÷ (1/100 + 1/200 + 1/300) = 1 ÷ (0.01 + 0.005 + 0.00333) = 1 ÷ 0.01833 ≈ 54.5Ω.
Frequently asked questions
How is Result calculated?
Result = 1 ÷ (1 ÷ [Resistance 1] + 1 ÷ [Resistance 2] + 1 ÷ [Resistance 3]).
Is the Parallel Resistance free to use?
Yes — every calculator on Simple Calculator Tools is free, runs in your browser, and does not require an account.
Parallel Resistance
Combined resistance = 1 ÷ (1/R1 + 1/R2 + 1/R3). The reciprocal of combined resistance equals the sum of the reciprocals of each individual resistance.
Let's understand your parallel resistance result.
Calculate a result above and this guide will help you interpret it using this calculator's own formula and explanation.
Pro Tips for Parallel Resistance
- Combined parallel resistance is always lower than the smallest individual resistor's value — a useful sanity check on your calculation.
- For just two resistors, the simpler formula (R1×R2)/(R1+R2) gives the same result without needing the reciprocal-sum approach.
Common Parallel Resistance Mistakes to Avoid
- Forgetting that combined parallel resistance is always less than the smallest individual resistance — a result larger than the smallest input resistor indicates a calculation error.
When to Use This Calculator
This calculator finds the combined resistance of up to three resistors wired in parallel — a fundamental electrical circuit calculation.