Parallel Resistance Calculator

1/R = 1/R₁ + 1/R₂ + … — find equivalent resistance of resistors in parallel.

Inputs

Result

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General calculation reads

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Scientific calculator (Casio fx-991EX)
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How to use this calculator

  • Enter resistance values separated by commas.
  • Read equivalent resistance.

About this calculator

Resistors in parallel: the reciprocal of total equals the sum of reciprocals. The equivalent resistance is always less than the smallest individual resistor. Special case: two resistors → R₁R₂/(R₁+R₂). Three or more identical R → R/n.

Frequently asked

Why is parallel R always smaller than the smallest?+
Because adding paths always lowers resistance — current flows through every available path. Mathematically, the reciprocal sum makes the result smaller.
How do parallel resistors share current?+
In inverse proportion to their values. Lower R takes more current. I_n = V / R_n where V is the same across all.
Do all parallel paths see the same voltage?+
Yes — that's the defining property of parallel circuits. Voltage across each branch is identical.
How to handle dozens of resistors?+
The calculator handles any count. For identical resistors of value R, R_eq = R/n.
What if one resistor is zero?+
A zero-resistance path shorts out everything else. R_eq = 0. The calculator skips zero-or-negative inputs to avoid division-by-zero.

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