Enter up to 10 resistor values (in ohms) into R1 through R10 and the Parallel Resistor Calculator computes the equivalent total resistance of your parallel circuit. You'll also see the conductance and a visual breakdown of each resistor's contribution. Leave unused resistor fields blank — only filled values are included in the calculation.
Equivalent Resistance
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Total Conductance
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Resistors in Circuit
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Smallest Resistor
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The equivalent resistance of resistors in parallel is calculated using: 1/R = 1/R₁ + 1/R₂ + ... + 1/Rₙ. You sum the reciprocals (conductances) of all individual resistors and then take the reciprocal of that sum to get the total equivalent resistance. For just two resistors, this simplifies to R = (R₁ × R₂) / (R₁ + R₂).
Adding a resistor in parallel creates an additional path for current to flow. Each new path increases the total conductance of the circuit, which means the overall opposition to current (resistance) decreases. The equivalent parallel resistance will always be less than the smallest individual resistor in the circuit.
For two resistors R₁ and R₂ in parallel, use the product-over-sum formula: R = (R₁ × R₂) / (R₁ + R₂). For example, a 100 Ω and 200 Ω resistor in parallel give R = (100 × 200) / (100 + 200) = 20000 / 300 ≈ 66.67 Ω.
Yes. In a parallel circuit, all resistors share the same voltage across their terminals — this is a defining characteristic of parallel connections. However, the current through each resistor differs based on its resistance value, with lower-resistance paths carrying more current.
If you know the total equivalent resistance R and one resistor value R₁, you can find the unknown R₂ using: R₂ = (R × R₁) / (R₁ − R). This works for two-resistor circuits. For more resistors, rearrange the full parallel formula: 1/R₂ = 1/R − 1/R₁ − 1/R₃ − ...
All resistance values are entered and displayed in ohms (Ω). Conductance — the reciprocal of resistance — is shown in siemens (S). If your resistors are in kilohms (kΩ) or megaohms (MΩ), convert them to ohms first by multiplying by 1,000 or 1,000,000 respectively.
This calculator supports up to 10 resistors in parallel simultaneously. Simply fill in the values for R1 through R10 as needed — any fields left blank are excluded from the calculation. The formula scales to any number of resistors using the sum-of-reciprocals method.
No. Parallel resistance cannot be zero unless one of the resistors has zero resistance (a short circuit), which would effectively bypass all other resistors and short the circuit. It also cannot be negative for standard resistors. The result will always be a positive value less than the smallest resistor in the group.