Parallel Resistance Calculator

About this calculator

When resistors are connected in parallel, the same voltage appears across each of them but the current splits between the branches, so the total (equivalent) resistance is always less than the smallest individual resistor. The relationship is 1/Rₜ = 1/R₁ + 1/R₂ + 1/R₃ + ... — the reciprocal of the total resistance equals the sum of the reciprocals of each resistor. For just two resistors this simplifies to the handy shortcut Rₜ = (R₁×R₂)/(R₁+R₂).

This calculator finds the combined resistance of two or three resistors wired in parallel. Electronics hobbyists, electrical engineers and technicians use parallel resistance calculations constantly when designing circuits — for setting a specific load resistance, combining standard resistor values to hit a non-standard target, calculating current-sharing in power distribution, or analyzing how adding a component to an existing circuit branch changes total impedance.