What size bike do I need?

The next step of buying a road bike is making sure that whatever you buy, you get it in the correct size. This can be as simple or as in-depth as you choose to take it, but it is possible to decathlon road bikes review make the wrong choice here, so be sure to follow our advice.

A size guide for the Specialized Allez

Specialized’s size guide is specific to each model it makes. In this case, the Allez is suitable for riders between 5ft1 and 6ft5 tall (Image credit: Specialized)
Simply, all bike brands will have a size chart for their bikes. This will be pretty basic, but perfectly functional for the majority of riders. It will break down the various sizes available into brackets based on your overall height (and sometimes leg length) so you can easily see which is most suitable for you. Put even more plainly, it will tell you that if you are X centimetres tall, then Y will be the correct size for you.

Bike size guide

Taking it a little further, bike brands will in most cases also supply a geometry chart that outlines the lengths of the bike’s tubes and key sizing metrics like the stack and reach of the bike. Read our detailed explainer for more information, handily titled “What size bike do I need?” as well as our separate explainer to bike fit, where you’ll learn how you can adjust and tailor a bike’s components to your specific fit requirements.

There are also tools on the internet that allow you to compare the geometry of two separate bikes, my favourite of these is Geometry Geeks.