How to Measure a Mountain Bike Frame?

four mountain bike frames leaned against a wooden fence

Knowing how to measure a mountain bike frame and choosing the right size for your height is paramount when it comes to comfort, control, and performance on the trails.

A mountain bike that fits properly will reduce the risk of injuries and boost your riding skills, which is why this step shouldn’t be taken lightly.

Before measuring your frame and using our online calculator to determine the right size for you, it’s important to be aware of the different types of MTB frames available.

Types of Mountain Bike Frames

mountain bike frame styles

There are three main types of mountain bike frames that you should be aware of:

  • Traditional (or Rigid): Rigid mountain bikes have no suspension at all. They are lightweight and require minimal maintenance, but they can feel bumpy to ride on rough sections.
  • Hardtail: Hardtail mountain bikes have a front suspension fork, but no rear suspension. They are perfect for beginners who don’t ride the most challenging trails, as they are generally lighter and more affordable than full-suspension bikes.
  • Full-Suspension: Full-suspension mountain bikes are the most complex of the three. They have both a front suspension fork and a rear suspension shock. They are the most capable on the trails, but are also the heaviest and the most expensive.

Now that we have that in the clear, let’s see how to measure them!

How to Measure a Mountain Bike Frame?

how to measure mtb frame

When it comes to measuring a mountain bike frame, the seat tube length is the most important metric. However, top tube length and standover height are important as well to get the correct fit.

Mountain bike frame sizes are expressed in inches, typically from 13″-24″, or in size classes, from XS to XXL. Of course, the measurements in inches are much more precise, but the sizing charts can still differ from manufacturer to manufacturer.

That’s why your safest bet is to measure the seat tube length of your mountain bike (from the center of the bottom bracket to the top of the seat tube) and use our online calculator to determine the rider height range.

To start measuring your mountain bike frame, first choose your style below:


What style mountain bike do you have?


Frequently Asked Questions

measuring mountain bike frame faq

1. How do I know my mountain bike frame size?

To determine your ideal mountain bike frame size, you should first measure your inseam length and height. After that, you can consult the bike manufacturer's frame size chart and compare your measurements to their recommendations. Alternatively, you can also use an online mountain bike frame size calculator.

2. What happens if a mountain bike frame size is too small?

If a mountain bike frame size is too small for your height and inseam length, the bike will feel uncomfortable to ride, and your performance on the trails will suffer. You will feel less confident while riding, and the small size may even lead to pains, aches, and injuries. 

3. How to measure top tube length?

To measure the top tube of a bike, you should start from the point where the top tube connects to the seat tube and measure across the top tube to the point where it connects to the head tube. For best results, measure from the center of the seat tube to the center of the headtube. 

4. How do you measure a full-suspension mountain bike frame?

A full-suspension mountain bike frame is measured based on the seat tube length and sometimes the top tube length as well. To determine the seat tube length of your full-suspension mountain bike, measure from the center of the pedal crank axle to the top of the seat tube. 

5. What size is a 17-inch mountain bike frame?

A 17-inch mountain bike frame is a frame with a 17-inch long seat tube. This size is also commonly known as a Medium size class, though this sizing method is not as reliable as using inches and actually measuring the length of the seat tube. 

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