About the Bike Chain Length Calculator
This bike chain length calculator tells you how long a new chain should be for a derailleur bike, using the chainstay length and the tooth counts of your largest chainring and largest rear cog. It returns the length in inches, the number of links rounded up to a whole inch (an inner and outer link pair), and how many links to remove from the chain in the box.
It is meant for home mechanics replacing a worn chain without the old one to copy, for anyone changing cassette or chainring size, and for frame builds where you are installing a drivetrain from scratch. Every modern bicycle chain has a half-inch pitch, so one inch of chain equals two links.
The formula is the long-standing workshop estimate of the "big-big plus one inch" method recommended by Park Tool and Sheldon Brown, with Park Tool's extra inch for wide-range 1x cassettes (largest cog 42T or more). Always confirm on the bike: shift to the big ring and biggest cog and check that the rear derailleur still has some forward room before closing the chain. Some 1x and 12-speed systems (for example SRAM Eagle) specify their own sizing method, which takes priority.
With the default inputs, the links needed is 110. Change any value above to recalculate instantly.
How to use the bike chain length calculator
- 1Measure the chainstay from the centre of the crank bolt to the centre of the rear axle.
- 2Choose millimetres or inches and enter the measurement.
- 3Enter the teeth on your largest chainring and largest rear cog.
- 4Enter how many links the new chain has to see how many to remove.
- 5Cut to the link count, then check the big-big gear on the bike before riding.
Formula and method
C is the chainstay length in inches, F the tooth count of the largest chainring and R the largest rear cog. The chain wraps the chainstay twice; each tooth on a sprocket holds half an inch of chain, and roughly half of each sprocket is wrapped, which is why the teeth are divided by four. A is the allowance: 1 inch (one full link pair) beyond the big-big wrap, as Park Tool and Sheldon Brown recommend, or 2 inches when the largest cog is 42T or bigger, following Park Tool's guidance for dedicated 1x systems.
Because a chain can only be joined at a full inch (one inner plus one outer link), the length is rounded up to the next whole inch and doubled to get the link count. Chainstay lengths entered in millimetres are converted at 25.4 mm per inch. The method assumes a derailleur drivetrain; single-speed and internally geared bikes are sized by axle position instead.
- L
- Chain length in inches
- C
- Chainstay length (bottom bracket to rear axle), inches
- F
- Teeth on the largest chainring
- R
- Teeth on the largest rear cog
- A
- Allowance: 1 in, or 2 in when R ≥ 42
Worked examples
Road bike, 420 mm chainstays, 50T ring, 32T cog
420 mm is 16.54 in, so 2 × 16.54 + 50/4 + 32/4 + 1 = 54.57 in. Rounding up to 55 in gives 110 links, so a 114-link chain needs 4 links removed.
1x mountain bike, 435 mm stays, 32T ring, 52T cog
435 mm is 17.13 in. With a 52T cog the wide-range 2-inch allowance applies: 34.25 + 8 + 13 + 2 = 57.25 in, which rounds up to 58 in or 116 links — 10 fewer than a 126-link chain.
Older road frame measured in inches, 53/28
2 × 16.25 + 53/4 + 28/4 + 1 = 53.75 in. That rounds up to 54 in, or 108 links, so remove 6 from a 114-link chain.
Frequently asked questions
How many links should my bike chain have?+
It depends on chainstay length and gearing. Typical road bikes need 106–112 links, while 1x mountain bikes with 50–52T cassettes often need 114–120. Use the formula or match the old chain if it was the right length.
Why must a chain have an even number of links?+
Chains alternate inner and outer plates, so a standard chain can only be closed by joining an inner link to an outer link. That forces lengths in whole inches, which is always an even number of half-inch links. Half-links exist but are rare on derailleur bikes.
What happens if my chain is too short or too long?+
Too short and shifting into the big ring and biggest cog can tear off the derailleur or hanger. Too long and the chain sags or slaps in the small ring and smallest cog, and may drop or skip when the derailleur runs out of take-up.
Should I count the quick link?+
Yes. A quick link replaces one outer link, so count it as one link when you size the chain. If you size with a connecting pin instead, the count is the same.
Does this work for SRAM Eagle or full-suspension bikes?+
It gives a good starting estimate, but SRAM Eagle and many full-suspension frames have their own procedure (often with the shock compressed to sag). Follow the manufacturer method when one is published.