CALCULATOR · CHAIN
Bike chain length calculator: the links your chain needs
Measure the chainstay (from the bottom bracket axle to the rear axle), enter the largest chainring and cog, and you get the links: 2 × chainstay + chainring ÷ 4 + cog ÷ 4 + 1 inch, rounded to an even number. With 410 mm, a 52 chainring and a 32 cog it gives 110 links. Check it on the bike before you cut.
Check it on the bike before you cut.
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Examples
| Chainstay | Chainring | Cog | Inches | Links |
|---|---|---|---|---|
| 405 mm | 50 | 30 | 52.9 | 106 |
| 410 mm | 52 | 32 | 54.3 | 110 |
| 415 mm | 48 | 36 | 54.7 | 110 |
| 425 mm | 46 | 36 | 55.0 | 110 |
| 420 mm | 40 | 42 | 55.6 | 112 |
| 435 mm | 32 | 52 | 57.3 | 116 |
Where the formula comes from
A chain has a half-inch pitch and wraps about half of each sprocket. So each tooth wrapped adds 1/4 inch on each side, and the distance between the axles is covered twice:
inches = 2 × chainstay + chainring ÷ 4 + cog ÷ 4 + allowance
The allowance comes from Park Tool's method: go round the largest chainring and cog without passing through the derailleur, and add two rivets, which is one inch. With cogs of 42 teeth or more, four rivets, which is two inches. Park Tool covers up to 36 and from 42 teeth; in between, the calculator adds one inch.
The formula is an approximation that ignores the chain's angle. Against the exact length of a belt round two sprockets, it falls short by less than 0.2 inches in these examples, less than one link. It then rounds up to an even number, because that is the only way a chain closes.
How to check before you cut
- If your old chain was the right length, lay it beside the new one and match them rivet by rivet. Bear in mind that the old one has lengthened.
- If not, run the chain round the largest chainring and cog without going through the derailleur, and add two rivets, or four with cogs of 42 teeth or more.
- If you use a quick link, fit half of it when counting: it adds half an inch.
- On a full-suspension bike, take the shock off and compress the suspension fully before measuring, because the distance between chainring and cog changes as it compresses.
In Pedalytics
Pedalytics is not out yet: it is listed as «Coming soon». When you change a chain, earlier rides stay tied to the old chain and the new one starts its own wear. To know when it is due, read when to replace the chain.
Frequently asked questions
How many links does a road bike chain have?
It depends on your bike: this formula gives 110 links with a 410 mm chainstay, a 52 chainring and a 32 cog. Chains are sold long and cut to size.
Why does it have to be an even number?
Because a chain alternates inner and outer links: closing it means joining one of each.
How do I measure the chainstay?
From the centre of the bottom bracket axle to the centre of the rear axle, in a straight line. If your bike has adjustable dropouts, measure with the wheel where you will ride it.
What happens if the chain is too short or too long?
SRAM warns that a wrong length affects shifting and can damage the bike or parts. Always check with the chain fitted on the largest chainring and cog before you cut.
Sources
Pages read when this text was written or revised, on 3 November 2026.
- Park Tool. Chain Length Sizing. Park Tool, 2015.
- SRAM. How do I determine the right chain length for my SRAM Eagle drivetrain?. SRAM, soporte.