Free bicycle chain length calculator. Enter chainstay length and gear teeth to estimate the chain length in links for your bike.
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Enter chainstay length in centimetres and the teeth on your largest chainring and largest rear cog. The calculator uses the Park Tool formula in inches, converts the result to links at a 12.7 mm pitch, and rounds up to an even link count. Always confirm the cut on the bike in the big-big combination before joining the chain.
The industry standard Park Tool chain length formula is L equals 2C plus F divided by 4 plus R divided by 4 plus 1, with everything in inches. C is chainstay length, F is the largest front chainring teeth, and R is the largest rear cog teeth. The 2C term covers the two straight chain runs, the F and R terms cover the wrap around each gear, and the final plus 1 is the derailleur inch the rear derailleur needs to tension the chain.
Divide the formula length in inches by 0.5, the pitch of one standard bike link, to get raw links, then round up to the next even number. The count must be even because a chain alternates inner and outer plates, and two ends of the same type cannot join. Count the master link as one full link pair when you join the chain. At 12.7 mm per link, the cut length in millimetres is simply links times 12.7.
Measure chainstay length in a straight line from the centre of the bottom bracket axle to the centre of the rear axle, not to the edge of the dropout. Frame geometry charts publish this figure in millimetres: typical road bikes run 405 to 415 mm, gravel bikes 420 to 435 mm, and mountain bikes longer still. Enter centimetres here and the calculator converts to inches for the formula.
The hands-on Shimano chain length method routes the chain over the largest chainring and largest cog without threading it through the derailleur, pulls the ends snug, and adds two links, which is one inch. Use this big-big method on the bike as a double check against the formula result. For full suspension bikes, size at maximum chain growth with the suspension compressed, or follow the frame maker link count.
Most derailleur bikes land between 104 and 122 links: roughly 106 to 112 for road bikes, 110 to 114 for gravel bikes, and 112 to 122 for mountain bikes. Your exact count comes from your own chainstay and gear sizes, so measure instead of copying a chart range. New chains ship with 114 to 126 links, so almost every new chain needs links removed with a chain tool.
A chain that is too long sags or slaps the chainstay in the small-small gears, and the derailleur cage folds back until the chain nearly touches itself. A chain that is too short feels guitar string tight in the big-big combination, and the shifter may refuse the biggest cog. If a brand new chain skips under power, suspect a worn cassette or chainring before blaming length.
Take a 42 cm chainstay, a 44 tooth chainring, and a 16 tooth cog. Chainstay in inches is 42 divided by 2.54, which is 16.54 inches. Length is 2 times 16.54 plus 11 plus 4 plus 1, which is 49.07 inches. Raw links are 49.07 divided by 0.5, which is 98.14, rounded up to the even count of 100 links, or 1270 mm.
Use the Park Tool formula: length in inches equals 2 times chainstay inches plus chainring teeth divided by 4 plus cog teeth divided by 4 plus 1, then divide by 0.5 and round up to an even link count.
Most bikes need 104 to 122 links: about 106 to 112 for road, 110 to 114 for gravel, and 112 to 122 for mountain bikes.
A chain alternates inner and outer plates, so an odd count leaves two ends of the same type facing each other and they cannot join.
Measure in a straight line from the centre of the bottom bracket axle to the centre of the rear axle, or read the figure from your frame geometry chart.
Almost always. New chains ship with 114 to 126 links, while most bikes need fewer, so remove the extra links with a chain tool.
Route the chain over the largest chainring and largest cog without the derailleur, pull snug, then add two links before cutting.
Too long sags and slaps in small-small gears. Too short feels tight in big-big and may stop the shifter reaching the biggest cog.
No. Speed sets chain width, from 7.1 mm at 6 to 8 speed down to 5.25 mm at 12 speed, but length comes from chainstay and gear sizes only.
Suspension movement lengthens the bottom bracket to axle distance as the wheel travels, so size the chain at maximum growth or follow the frame maker count.