Coupling Selection Calculator

This calculator estimates the torque a shaft coupling must be rated for, and recommends a coupling family based on how much shaft misalignment your installation will actually see. It starts from your steady-state transmitted torque and multiplies it by a service factor — a shock/overload margin ranging from 1.0-1.5 for smooth uniform loads up to 2.0-3.0 for heavy shock loads like reciprocating compressors or punch presses — to get a design torque, which is then converted to inch-pounds as the required catalog rating. Separately, it converts your torque and shaft speed into transmitted horsepower using the standard HP = T·RPM/5252 relationship, useful for cross-checking against a motor nameplate.

The coupling type recommendation is a rule-based lookup against your entered angular and parallel misalignment: tight tolerances (under 0.5° and 0.005") suggest a rigid or beam coupling, moderate misalignment suggests jaw or disc styles, larger misalignment points toward elastomeric or gear couplings, and anything beyond that falls back to a universal joint — these are commonly-cited industry guidelines, and real coupling families vary enough by maker that you should always cross-check the recommendation against that manufacturer's specific alignment charts. The coupling outer diameter and max bore are rough sizing estimates only, derived from an empirical curve relating bore size to design torque, meant to give a ballpark envelope for space planning — always verify final bore, OD, and torque rating against the actual manufacturer's catalog before specifying a part, since real coupling geometry varies significantly by design and material.