The Colorado Sportbike Club

Speed Calculator

Determine your motorcycle's speed in a specific gear at a certain RPM
Thinking about changing your sprocket gearing but wondering how it's going to affect your top-end?
Or, do you want to know your bikes top-speed without breaking the law?
This page can help!

To use this calculator, you will need the Primary Reduction Ratio, Final Reduction Ratio and individual gear ratios.
These should be in your owners manual.

Example: Kawasaki ZX-11
Rear Wheel Diameter in Inches   17
Rear Tire Size - First Number (ie: 180/55)   180
- Second Number (ie: 180/55)   55
Primary Reduction Ratio*   1.6379
Final Reduction Ratio**   2.6471 (stock:45/17)
Gear Ratio* (for one of your gears)   1.0357 (6th)
RPM   11500
* Ratios can be calculated by dividing the larger number by the smaller number
** Final Reduction Ration is based on the number of sprocket teeth (rear divided by front)
Disclaimer: The speeds calculated here are based on tire circumference and gearing.
We do not guarantee that they will match your speedometer or police radar.

If you experience any problems with this page, or this calculator does not work for you,
please contact