How do I determine the right chain length?

The most reliable method is: wrap the chain around the largest chainring and largest cog without going through the derailleur, then add 2 links (1 inch). Alternatively, use the Shimano formula based on chainring teeth, cog teeth, and chainstay length. Always check by shifting into the biggest-biggest combination.

What happens if my chain is too long?

A chain that is too long will not maintain proper tension in small-small gear combinations, leading to chain slap, dropped chains, and poor shifting. The rear derailleur cannot take up the slack properly. On rough terrain (common in bikepacking), this is a recipe for mechanical problems.

What happens if my chain is too short?

A short chain is dangerous — shifting into the big-big combination can damage the rear derailleur, break the chain, or crack the derailleur hanger. On a bikepacking trip, this can end your ride. Always ensure the chain can reach the largest chainring and largest cog with slight slack.

How often should I replace my chain?

Check chain wear with a chain checker tool. Replace when stretch reaches 0.5% (0.75% for 11/12-speed). Most chains last 3,000-5,000km in dry conditions, less in wet or dirty conditions common in UK bikepacking. Replacing chains regularly extends cassette and chainring life significantly.

CampCalcs

Chain Length Calculator

Calculate the correct chain length from chainring sizes, cassette range and chainstay length.

Largest Chainring

Smallest Chainring

0 for single chainring

Largest Rear Cog

Smallest Rear Cog

Chainstay Length

Measure from BB centre to rear axle

How We Calculate This

Chain Length Formula

Links = (Large chainring / 2) + (Large cog / 2) + (2 x Chainstay inches) + 1

Result is rounded up to the nearest even number (chains need even link counts for standard connecting links).

Chain Pitch

Standard bicycle chain pitch is 12.7mm (1/2 inch) per link.

Frequently Asked Questions

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Last updated: February 2026

All calculations are estimates. Always verify conditions and use proper safety equipment outdoors.