Mountain Bike Frame Size - What MTB size do I need?

When buying a new mountain bike, you will have to make several choices. Do you want a hardtail or a full suspension MTB? Do you prefer a SRAM or a Shimano groupset? Once you have found the make and model that meets your needs and wants, perhaps the most important question is asked: What frame size do I need? One general way to determine your MTB frame size is to use rider height. For some people, however, this is not enough and other yardsticks are used as well. In this blog, we will discuss what you need to determine the right frame size so you can enjoy your new MTB to the fullest!

When buying a new mountain bike, the frame size is extremely important. Riding on an MTB that is just a bit too small or big for you can cause all sorts of injuries, from saddle soreness to pain in your knees, feet, back and neck. As a mountain biker, you want to ride as smoothly and comfortably as possible, which is why your bike’s frame size simply has to be right.

Standard MTB size chart

There is a standard chart of mountain bike sizes, in which the rider’s height is linked to a particular frame size. An important note regarding the size chart below is that these indications are not the same for every person and vary from brand to brand. Here we include the sizes provided by Trek, Scott, Cube and Cannondale.

How to calculate the right MTB size

The frame size of an MTB really refers to the length of the seat tube. More precisely, this is the distance in centimetres between the top of the frame and the centre of the bottom bracket. However, the seat tube length alone is not at all enough to determine your frame size because it says nothing about the other dimensions of the bike in question.

Mountain bike geometry can vary greatly from brand to brand, which is why it is important to look at other dimensions besides seat tube length. As the above chart shows, an L size, for example, is different for one brand than another.

MTB geometry

You cannot always deduce the right frame size from your height. If you have different body proportions or an aggressive riding style, you need a different size. You can determine the size that is right for you using some useful indicators, important ones being the mountain bike’s stack and reach.

Measure stack

The stack of your mountain bike is strongly related to your riding style. The stack height is the distance between the centre of the bottom bracket and the top of the head tube. If you prefer an aerodynamic position, the handlebars should be as low as possible to allow you to lean forward very far.

Do you prefer to sit more upright on your bike? Then you can raise the handlebars a bit, increasing stack. This decreases aerodynamics but lets you sit on the bike without getting pain in your back.

Measure reach

The reach of a mountain bike is also related to riding style, and is the distance from the head of the handlebars to the axle of the bottom bracket. The longer the reach, the deeper you sit. A very long reach means a very aerodynamic and aggressive riding style. So if you know your preferred riding style, you can choose a mountain bike with an accordingly long or short reach.

If you are looking for a more comfortable mountain bike, choose a frame with a shorter reach. It will let you sit more upright, which is more relaxing. So, if you are mainly a recreational mountain biker whose focus isn't so much on setting the fastest time, you should opt for a shorter reach.

Fine-tune your MTB riding position

If you are not completely comfortable on your mountain bike, it does not necessarily mean that you have the wrong frame size. You can also improve your riding position by changing your saddle or handlebar position. So, for example, if you move your saddle slightly forward you will sit a bit more upright, which can be more comfortable.

Make the right choice

We hope that all this information will help you choose the right MTB frame size. If, however, you still have doubts about the right size for your mountain bike, get help from a competent salesperson or have a bikefit done by a professional. This way, you are sure to buy the MTB that suits you best!