Roller Chain Sprocket Diameter Calculator

Sprocket Diameter according to ASME B29.1.

  • Dr = roller diameter
  • N = number of teeth
  • P = chain pitch
  • PD = pitch diameter

Pitch diameter of sprocket = P / Sin (180deg / N)

Bottom diameter of sprocket = PD - Dr

Caliper diameter for even number of teeth = bottom diameter

Caliper diameter for odd number of teeth = PD x (Cos (90deg/N) - Dr

Tolerances on caliper diameter of sprockets :

  • Plus tolerance = 0.000
  • Commercial minus tolerance = 0.002xPx N^(0.5) + 0.006, in.
  • Precesion minus tolerance = 0.001xPx N^(0.5) + 0.003, in.

Approximate outside diameter of turned sprocket = P x (0.6 + cot (180deg/N))

Outside diameter of topping hob cut sprocket = PD − Dr + 2WD

Maximum hub and groove diameter (MHD ) of sprockets = P x (cot (180deg/N)-1)-0.030, in.

Roller Chain Sprocket Diameter Calculator:

Chain Pitch [P] in
Number of teeth [N]  
Roller diameter [Dr] in

Note: Use dot "." as decimal separator.


Pitch diameter of sprocket in
Bottom diameter of sprocket
Caliper diameter
Caliper diameter plus tolerance
Caliper diameter commercial minus tolerance
Caliper diameter precision minus tolerance
Approx. outside diameter of turned sprocket
Max. hub and groove diameter (MHD) of sprockets



  • ASME B29.1-2011 - Precision Power Transmission Roller Chains, Attachments, and Sprockets