Appleblock: Cycle Designs and Ideas > web tools

half-step gearing cog and chainring designer

Page created April 24, 2010 by Garrett Belmont, with infographics advice from James Black.

Update April 30, 2010 - Many thanks to Mike Sherman for finding the error in the code. Calculator now works in Firefox.

Update March 11, 2015 - Check out Joe's combined tools page utilizing Mike Sherman's site and Apple Block.


Note: Best used for 5 or 6 speed cog sets. 7 and 8 speeds added for fun. Tips: To find a desired cog set (perhaps one you already own) make small adjustments to the percentage and gear inch. To find particular chainrings, adjust percentage, gear inch, and smallest cog.

Wheel diameter (inch). 27 works well for 700c (700x32), and 26 for 650b.
Smallest cog (teeth)
Ratio jump (percent). If 10 is desired, experiment by trying 9.5 or 10.5.
Approximate highest gear inch

5 speed
6 speed
7 speed
8 speed