Bike Chain Length Calculator

The correct chain length

It really isn’t too difficult to get the chain length right. All you need are a chain rivet or a chain lock and you will need to know the amount of chain links needed for a correct chain length. You can use either of these two methods: Take your old chain and lay it out next to the new one. Now you know exactly how long the new chain should be and you can detach the links you don’t need. But what if you are building a new bike or you don’t have an old chain for reference?

One way to be absolutely sure is to use our calculator to find the exact number of chain links needed. There is, however, a trick you could use if you haven’t got a calculator at hand. Place the chain over the largest sprocket and the largest chain ring and bring the ends together without routing the chain through the derailleur. Count four more chain links to the length and detach the links you don’t need at that point. Link the two ends of the new chain and voilà: a chain of the correct length is ready. This method also works pretty well on exotic bike types (e.g. recumbent bikes), where the chain gets rerouted again.

Next we will look at why it is so important to have a well-fitting chain, how to mount it correctly and how to maintain it properly.

The bike chain

The bike chain is the central element for propulsion. It consists of individual outer and inner plates that are held together with studs or bolts. The chains are lubricated to improve the movement of the links and to make them more resistant to dirt.

There are various standard types that have developed over time. The important thing to know is whether a chain is meant for 9, 10 or 11 speed derailleurs. The number indicates how many gears the derailleur can switch and the chain will need to be wider or narrower according to that number.

There are also various chain types available for chains for mountain bikes and road bikes, which differ in weight and stability. Some chains are optimised specifically for improved switching performance and can only be mounted in one particular direction.

Chain ring, sprocket and chain stay

The size of these elements is the most important factor for calculating a chain length. After all, it makes sense to think that a longer chain stay will also need a longer chain. In addition to that, you need to consider the number of teeth on the largest chain ring and largest sprocket, because the chain will be pulled the tightest in such a configuration.

Problems due to worn and incorrectly set chains

Heavily worn chains not only slow down gear shifting, they will also wear down the chain rings and sprocket set a lot faster, which means they will have to be changed more frequently. If the newly mounted chain is too long, then it will hang – which will also negatively impact gear switching performance. If it is too short, it can damage the derailleur hanger and the rear derailleur due to too much tension.

Replacing the chain

Replacing a bike chain is not rocket science. You just need the right bike tool – specifically a chain tool. With it, you can remove the studs or bolts from the chain links or press them in again when you are finished. The tool is also great for shortening a chain to the correct length. A bike stand is also very helpful for removing the rear wheel, making it easier to mount a chain and allowing you to stand upright, which is much easier on your back. Chains with a chain lock can be opened with a special pair of pliers.

A chain of the correct length with have the right tension after mounting. Some rear wheel suspensions offer a little leeway for mounting the wheel. That will allow you to easily tighten the chain after mounting. You should, however, not tighten the chain over and over again, because that will make it slowly wear down, as the interplay with the sprocket will not remain sufficient over time.

Cleaning a bike chain

It is advisable to clean and oil the chain regularly, because it is always out in the open and will have to deal with all kinds of weather, dirt, dust, mud and even road salt. A really dirty chain will benefit from some mildly soapy water or chain cleaner to get rid of the most stubborn dirt. Be careful with aggressive grease removers! It could eat away at the base lubricant of the chain.

Make sure to thoroughly rinse the chain in cold water to remove any residual cleaner, pull the chain through a dry cloth and leave it to dry completely. Only then will the lubricant adhere to the chain properly. Next, you need to apply the chain oil. There are all-rounder versions as well as specialised lubricants for wet and dry conditions. The best thing is to hold a cloth underneath so nothing drips onto the floor or the wheels and of course: watch out for the brake discs.

Once the chain is well lubricated, leave the chain to rest for around half an hour. Pull the chain through a lint-free cloth again to get rid of any excess grease – and voilà, the chain is (almost) good as new.

Pointing a garden hose at the chain is not recommended, as some parts (like the derailleur) could be displaced under the pressure of the water.

Determining level of chain wear

We already talked about the fact that the sprockets and chain rings could get damaged by a worn chain. Not to mention sluggish gear switching. A so-called chain gauge will help you determine whether or not a chain needs replacing. A chain gauge usually has two side: one for steel/titanium and one for aluminium sprockets and/or chain rings. It is very easy to use: Place the gauge onto the chain; if it sinks in completely, then you should replace the chain as soon as possible.

Any rule of thumb regarding replacing a chain after a specific number of miles is tricky, because there really are too many factors that contribute to wear. A chain on a bike used all winter long may have to deal with plenty of road salt and will therefore wear a lot faster – but with proper care and maintenance, it could probably do 1500 to 2000 miles with ease.