Chain Length Calculator

The Shimano method is the industry-standard method for calculating chain length. It converts your chainstay measurement from millimeters to inches, then factors in the sizes of your largest chainring and largest cog to determine how many links you need. For related drivetrain setup, see our gear ratio calculator and crank length calculator.

The formula is: 2 × chainstay (inches) + largest chainring ÷ 4 + largest cog ÷ 4 + 1. The result is rounded up to the nearest even number because chains must have equal numbers of inner and outer links. Each link pair has a pitch of 12.7mm (½ inch), so the total chain length in millimeters is simply the link count multiplied by 12.7.

A worn chain accelerates cassette and chainring wear, leading to expensive drivetrain replacements. Use a chain wear checker tool regularly: replace the chain at 0.5% elongation for 11 and 12-speed drivetrains, or 0.75% for 10-speed and below. Most road chains last 2,000–3,000 miles, while mountain bike chains in wet conditions may need replacing every 1,000–2,000 miles.

When installing a new chain, always use this calculator to verify the correct number of links rather than matching the length of your old, worn chain. Worn chains elongate over time, so copying the old length results in a chain that is too long.