Chain Length Calculator
Calculate the correct bicycle chain length in links, based on your chainstay length and the number of teeth on your largest front and rear sprockets.
Why Chain Length Matters
A bicycle chain that is too short can’t shift into the largest gear combinations and may damage the derailleur, while a chain that is too long shifts poorly and can derail. Chain length depends on your frame’s chainstay length and the size of your largest chainring and cassette sprocket.
The Formula
This calculator uses the widely used Sutherland’s Handbook formula: L = 2C + (F + R)/4 + (F – R)² / (4π²C), where C is the chainstay length, F is the number of teeth on the largest front chainring, and R is the number of teeth on the largest rear sprocket, all converted to inches. The result is divided by the standard chain pitch of 0.5 inches and rounded to the nearest even number of links, since bicycle chains must have an even number of links to close properly.
Practical Notes
This formula gives a reliable starting length for a new chain, but always check that the derailleur cage can still take up slack in your smallest gear combination before cutting, and consult your derailleur manufacturer’s specific sizing guidance when in doubt.