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Calcimator

Coupling Selection Calculator

Select a shaft coupling by calculating design torque with service factor, required rating, and recommended coupling type based on misalignment.

Inputs

ft·lb
RPM
in
°
in

Results

Design Torque

750 ft·lb

Recommended Type

Jaw or Disc

Required Rating9,000 in·lb
Coupling OD (est.)5.8 in
Max Bore Diameter2.61 in
Transmitted Power171.36 HP
How to Use This Calculator
  1. Enter the steady-state Transmitted Torque in ft·lb — calculate it as T = 5252 × HP / RPM if starting from motor power.
  2. Set the Shaft Speed in RPM and the Shaft Diameter in inches (use the larger shaft if the two sides differ).
  3. Enter the expected Angular Misalignment in degrees and Parallel (Offset) Misalignment in inches.
  4. Set the Service Factor based on load type: 1.0–1.5 for uniform loads, 1.5–2.0 for moderate shock, 2.0–3.0 for heavy shock.
  5. Review the Recommended Type (Rigid, Jaw, Elastomeric, etc.) and the Required Rating in in·lb to match against catalog data.
  6. Confirm the Coupling OD estimate and Max Bore Diameter are compatible with your shaft and housing clearances.

How the result changes with Transmitted Torque

Transmitted TorqueDesign TorqueRecommended Type
50,00175,001.5 ft·lbJaw or Disc
175,001262,501.5 ft·lbJaw or Disc
325,000487,500 ft·lbJaw or Disc
450,000675,000 ft·lbJaw or Disc

What each input means

Transmitted Torque
Steady-state torque transmitted through the coupling. T = 5252 × HP / RPM.
Shaft Speed
Operating speed of the connected shafts. Higher speeds require better balance.
Shaft Diameter
Diameter of the shaft to be coupled. Both shafts should be similar size; use the larger one.
Angular Misalignment
Maximum expected angular misalignment between shaft centerlines. Rigid couplings allow ~0°; flexible allow 1-3°.
Parallel (Offset) Misalignment
Maximum parallel offset between shaft centerlines. Elastomeric couplings handle 0.01-0.03".
Service Factor
Multiplier for shock and overload protection. Uniform load = 1.0-1.5; moderate shock = 1.5-2.0; heavy shock = 2.0-3.0.

How this is calculated

Worked example, using the default values

  1. Identify Input Parameters
    4 parameters
    Transmitted Torque = 500, Shaft Speed = 1800, Shaft Diameter = 2, Angular Misalignment = 1 = 6 input(s) provided
  2. Calculate Design Torque
    Design Torque
    750 = 750
  3. Calculate Recommended Type
    Jaw or Disc = Jaw or Disc
  4. Calculate Required Rating
    Required Rating
    9000 = 9000
  5. Calculate Coupling OD
    Coupling OD
    5.8 = 5.8

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