The Amazing Sprockulator™
Sprocket change calculator

  1. All default values are for a standard GPZ 1100.
  2. Enter the new front and rear sprocket sizes.
  3. Select the gear, rpm and speed you would like to see the change in.
  4. Click on the Calculate button to see the change in speed at a constant rpm in a given gear as well as the change in rpm at a given speed.
  5. For results in a different gear, different rpm or different replacement sprocket sizes, just change the appropriate figure - the page will automatically recalculate.

Front   Rear
Primary reduction ratio:
1st gear ratio: 2nd gear ratio:
3rd gear ratio: 4th gear ratio:
5th gear ratio:

6th gear ratio:

Rear tyre circumference:

Original secondary reduction ratio:
New secondary reduction ratio:

Change in speed at given RPM

Original speed @  rpm = km/h or mph
New speed @  rpm = km/h or mph
which is a difference of 

Change in RPM at given speed

Original rpm @ 
= rpm
New rpm @ 
= rpm 
which is a difference of 

Thanks to Metro Yamaha in Brisbane, Australia for getting me started.