Bike Chain Length: Links From Chainstay and Gearing
A chain that is too short strains the derailleur and one that is too long sags. The standard formula gets the length close before you fit it.
What is the Chain Length Calculator?
Enter chainstay length in millimetres plus chainring and cog teeth. The tool applies the standard chain-length formula and rounds up to an even number of links. It is an estimate: always check the fitted chain on the bike before cutting.
How to use it
- Enter chainstay length in millimetres.
- Enter the largest chainring and cog teeth.
- Click Calculate Chain Length.
Worked example
With a 420 mm chainstay, 50-tooth chainring, and 28-tooth cog: 2 x 33.07 + 19.5 + 1 = about 86.64 links, rounded up to 88 links.
How long a chain for 420 mm stays, 50 x 28?
About 88 links, from an unrounded 86.64 links rounded up to an even number.
Frequently asked questions
Why round to an even number?
Chains join in pairs of links, so the fitted length must be even.
Should I cut exactly to this?
Use it as a starting length and check derailleur tension on the bike before cutting.