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Bicycle Chain Length Calculator

Chain Stretch/Wear Test


Bicycle Chain Length Calculator

Chain Wear/Stretch Check - Don't let a worn chain ruin your cassette and chain rings

Do You Really Need All Gears?

See Also


Ever wonder how to determine the correct length chain to use for your bicycle?  Are your chain problems due to a chain that is too short or too long?

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Chainstay Length
Note: If the bike has rear suspension, then this is the longest possible length.


   Inches cm
Front BIGGEST ring number of teeth.




Rear Cassette BIGGEST gear number of teeth.
This is the biggest (slowest) gear that you want to be able to shift into when in the biggest (fastest) ring on the front.  Do you need to be able to shift to all rear gears when in the big chain ring?

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Disclaimer: Always check to make sure the results are correct (preferably with an old chain) before breaking your good chain.  We are not responsible for any errors in the calculation or mistakes.  If you are not sure, add a few extra links, try it, and then shorten as needed.
Chain Length  
Chain Length (links)  

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See Park Tools  for more information about chain sizing.

Chain Stretch/Wear Check

Don't let a worn chain ruin your cassette and chain rings.
A worn/stretched* chain does not mesh properly and will quickly wear the teeth of your drive train making them nice and pointy.  After this has happened, if you put a new chain on, it will most likely skip on the old drive train.  The only thing you can do at this point is replace the chain rings and cassette (or take up jogging).

Here's an easy way to check your chain wear.  It can be done with the chain on or off the bike.

Click to Enlarge

Take a ruler (inches) and line up a chain pin on the 1-inch mark.

Click to Enlarge

Stretch the chain tight and look at the 13-inch mark.

A new chain should line up exactly with a chain pin. [See Picture]

If the stretch is 1/16" or less, [See Picture] you're in good shape.

If it's between 1/16" and 1/8", you should replace your chain.

If it is over 1/8", [See Picture] you'll probably need to replace not only your chain, but also your cassette and chain rings.

For those anal types (like me), Park Tools makes a wear gauge that lets you measure the wear.  Just slip it on to the chain and it tells you how worn your chain is.  It doesn't get much easier than that.  It'll pay for itself several times over the first time it saves a drive train replacement.

* Note 1: The chain doesn't actually stretch.  The rollers wear out, making the chain longer.  This gives it the appearance of having stretched.

Note 2: I've known people who take a different approach.  They simply run their chain until it fails.  Then replace the chain cassette and rings all together (by that time the cassette and rings are usually too worn to work with a new chain).  They figure the money they save on chains will help offset the cost of the new components.  But, unless you're using really expensive chains, I don't think the math works out for this.


Weight Lifting and Cycling
Want to start an argument?  Go to a group of cyclists and ask whether a cyclist should train with weights or not.
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Do you really need to be able to shift to all rear gears when in the big chain ring?

I find that shifting is improved on a mountain bike by running a shorter chain that is sized as if the middle front ring was the largest ring and using the shorter (long cage) rear derailleur instead of the more typical super-long cage used for mountain bikes.  However, the shorter chain won't shift into the largest (slowest) rear gears when in the big ring.  And the shorter cage will have too much slack when in the granny (smallest front ring) and smallest (fastest) rear gear.  However, this shouldn't be a problem, since you really shouldn't be using these combinations anyway.  Just be aware of these limitations and avoid attempting to shift into them.

Disadvantages:  (Read and heed these warnings)

  • You will not be able to use big cogs (rear wheel large granny gears) with the big ring (front fast gear).
  • If you try to shift into the now illegal big ring combinations, you risk breaking your chain, derailleur, hanger, etc.
  • If using the shorter derailleur cage, if you try to shift into the now illegal granny ring combinations, you risk dropping your chain due to the excess slack.
  • Do this at your own risk!


  • Crisper, faster, more reliable shifting.
  • Can use a shorter rear derailleur cage.
  • Less chance of over shifting (changing two gears when you only clicked one gear at the shifter).
  • Less chain slap.
  • Less chain weight.
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2006-03-26 Anonymous, Serious Competitor, age 50-59, wrote
Interesting, Factual

2006-03-27 Anonymous, Weekend Warrior, age 40-49, wrote
Interesting, Factual
You might note that when running a short chain, it may be difficult to prevent the upper jockey wheel from contacting the large cog, even if the 'B' adjustment is used.

2006-04-20 Anonymous, Industry pro, age 20-29, wrote
Interesting, Factual
Add somthing about keeping the chainline as straight as possible and the resulting effects on efficiency and chain wear.

Your way for determining chain length may work, but is unneccessarily complicated.

All you need to do is manually wrap the chain round the big chainring and biggest sprock, bypassing the rear deraillear. Where it then meets up +1 link is the chain length.

This doesn't work for a full bouncer (you could guess +2 links) but then how does someone work out maximum chainstay length for your method?!

Sitting at work with time to kill.......hence the reply!? Nice web page btw

2006-07-08 Weekend Warrior, age 50-59, wrote
Interesting, Factual

2006-08-05 Weekend Warrior, age 20-29, wrote
Interesting, Factual

2006-08-14 Paul Chappin, Weekend Warrior, age 30-39, wrote
Interesting, Factual
Easy way to tell if the chain is old. Better than buying a chain wear tool or taking the bike to you LBS. Thanks.

2006-09-26 ccy, Beginner, age 20-29, wrote
how the manufacturing process to make the chain?

2006-12-04 Joe, Weekend Warrior, age 40-49, wrote
I have been riding bikes since I was 5 years old and until recently, never experienced a broken chain. My son broke the chain on his bike the other day. Do you know where I can get a chain tool or what the cost of a new chain is?

epicidiot reply: Welcome to the world of bike maintenance.  Your local bike shop is probably your best bet for a new chain and chain tool. If you rarely change chains, it may even be worth it to have them install the chain as well. Chains are typically $15-30 depending on the quality, although even the cheapest are fine for general riding. If you like to clean your chain, get one with a removable link, such as the SRAM Power Link chains, so that you can easily take the chain off the bike.  Make sure the chain you get is the same speed (or higher) than the bike you are installing it on.  A 9-speed (the number of gears on the rear cassette) chain will work on an 8-speed bike, but not vice versa.  The best book I've found for the average guy on bike maintenance is Zinn & Art of Mtn Bike Maintenance.



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