Everyday chain length problems come down to one relationship between 3 figures. This calculator takes chain stay length, largest front chainring, largest rear cog and turns them into number of links in shortest possible chain and shortest possible chain length, with the working shown so you can check the result rather than simply trust it.
What Is the Chain Length Calculator?
It is built around number of links in shortest possible chain, shortest possible chain length, number of links, and it works the same way whether you are checking a homework answer, confirming a colleague's figure, or working something out for yourself. Everything runs in your browser, so nothing you enter is uploaded anywhere.
How the Chain Length Calculation Works
The calculator works through the relationship one step at a time, so a change in any input flows straight through to the result.
The relationship between chain stay length, largest front chainring, largest rear cog and number of links in shortest possible chain, shortest possible chain length, number of links, chain length is fixed, so the same figures always give the same answer. That makes it a good cross-check: run the numbers a second way and see whether the result agrees.
Getting a Result You Can Trust
For anything that matters, write the inputs down next to the result. A calculation you can reproduce is worth far more than a number you cannot explain, and it takes a moment to record chain stay length and largest front chainring and largest rear cog alongside number of links in shortest possible chain, shortest possible chain length, number of links.
Frequently Asked Questions
What do I need to work out number of links in shortest possible chain?
Enter chain stay length, largest front chainring, largest rear cog. The calculator then works through the relationship and reports number of links in shortest possible chain, shortest possible chain length, number of links.
What does the chain length actually calculate?
It takes chain stay length and largest front chainring and largest rear cog and converts them into number of links in shortest possible chain, shortest possible chain length, number of links using the standard relationship for this problem. Each step is applied in turn, so every output is traceable back to the numbers you typed in.
How should I enter chain stay length?
Use the value you actually have, in the unit shown next to the field. Enter every value in the same unit system. The calculator assumes the figures you supply are consistent, so it cannot correct a mistake that happens before the calculation starts.
Why does a small change in one value move the answer so much?
That happens when an output depends on a ratio, because dividing by a small number magnifies any change in it. Check the units first, then check whether the value you entered is in the range the relationship was designed for.
Can I use this for a quick estimate as well as a precise answer?
Yes. The calculator is built for quick checks, so round your inputs to a sensible number of significant figures and the result will be just as useful. If you need more precision, keep the same method and add digits to the inputs rather than adjusting the method itself.