This calculator gives the chain length to cut for a single-speed, fixed-gear or derailleur bike. Pick your drivetrain, enter your chainstay length and the tooth counts, and it returns the length in links and inches.
Bike Chain Length Calculator
Estimate chain length for single-speed or derailleur bikes from chainstay length and tooth counts.
How to use this tool
- Pick the drivetrain. Single speed and fixed gear, a derailleur bike whose largest cog is 36 teeth or fewer, or a 1x drivetrain with a 42-tooth or larger cog. For 37 to 41-tooth cogs, use your derailleur maker’s rule or the big-big wrap.
- Measure the chainstay from the center of the bottom bracket to the center of the rear axle, in millimeters. On a single speed, push the wheel all the way forward in the dropouts first.
- Enter the tooth counts. For a derailleur bike, use the largest chainring and the largest rear cog.
How it calculates
For derailleur bikes the tool uses Park Tool’s chain equation: twice the chainstay in inches (to the nearest 1/8 in), plus a quarter of the chainring teeth, plus a quarter of the cog teeth, plus 1 in. It rounds to the nearest inch, and 0.5 rounds up. A 1x drivetrain with a 42-tooth or bigger cog gets 2 in instead of 1. Park’s own example, a 16 3/8 in chainstay with a 42T ring and a 32T cog, gives 104 links.
For single speeds the tool rounds up to the next whole inch, so the chain fits with the axle forward and you can slide the wheel back to tension it.
Check before you cut
If your derailleur maker publishes its own sizing rule, use it instead. That applies to SRAM Eagle and Shimano 12-speed MTB groups and to full-suspension bikes. Before you cut, wrap the chain around the largest ring and largest cog to confirm the length. Our bike chain length guide lists each maker’s rule.
