How to Measure a Mountain Bike Frame

Looking for tips on how to measure a mountain bike frame? You’ve come to the right place!

If you’re in the market for a mountain bike then you know how important it is to ensure that it’s the proper size to suit your needs.

The good news is that mountain bikes are available in a wide range of different sizes which are pretty easy to measure.

But first, you must learn how to measure the different parts of the bike and understand what these measurements mean.

How to Measure Frame Size on a Mountain Bike

Safety is one of the most important considerations to make when riding your bike up in the mountains because you’re cycling through some of the most precarious terrains in the world.

That’s why it’s essential to learn how to measure a mountain bike frame so that you’re confident that you’re using the right bike.

One way to get proper measurements for your bike frame is to use the following tips provided below. It doesn’t matter if the measurements are expressed in inches or centimeters so long as they’re accurate.

Before you start measuring the frame, make sure the bike is standing on a level surface so that the back and front wheels are straight.

1. Measure the Length of Seat Tube

First up, you must determine the length of the seat tube. This refers to the distance between the seat tube joint and the crack center as well as the top tube.

2. Check the Top Tube Length

The length of the topmost part of the tube is the main tube that attaches the seat tube to the head tube.

In order to measure this part of the bike, simply put your tape measure right in the middle of the tube connecting the top tube to the head tube.

Make sure the tape measure is extended in order to cover the seat tube and the top tube joint. Write down the resulting measurements either in inches or centimeters.

3. Go Through the Head Tube Length

The length of your bike’s head tube can be measured using a normal tape measure placed between the joint connecting the head tube to the top tube, as well as the joint connecting the head tube to the front fork.

As for the head tube, it will determine the level at which your handlebars should be, whether high or low depending on your needs.

It doesn’t matter if your lightweight Mongoose mountain bike has a traditional or sloppy frame, the head tube length will be the same.

Sloping Top Tube and Sloping Seat Tube

A tape measure and a spirit lever are the two essentials required for anyone whose bike has a sloping top tube. Make sure that the rear and front wheels are on the same level.

Use the spirit lever to figure out how to get a straight line from the seat post’s front fork to the joint on the head tube.

Make a dot on the line that meets the seat post and measure the distance between the front fork joint and the head joint using your tape measure and make a dot on the seat tube.

In order to measure a sloping seat tube, all you need is to figure out the distance between the seat tube mark that you made before and the crank bolt center in order to determine the sloping top tube.

Frame Sizes

Most mountain bike frames measure 15 inches, 17 inches, and 19 inches respectively. These measurements translate to small, medium, and large sizes. Other sizes are available and include small and extra-large.

Depending on the manufacturer, you might notice a unique sizing chart for each option. For best results, round out the measurement of your bike frame to the nearest inch and compare it to the measurements on the manufacturers’ website.

Frame sizes are typically shown in 2-inch increments. It’s important to note that some manufacturers might have a 17-inch bike frame with a 22-inch top tube while another would pair a 23-inch top tube to a 17-inch bike frame.

The most important thing to keep in mind when looking for the right bike frame size is to give it a test drive to figure out what works best for you and see if it can handle you attaching things such as a bottle cage or hydration pack for your bicycle.


As you can see, it doesn’t take much to learn how to measure a mountain bike frame size. All you need is an understanding of your needs, including your height, your riding style, and the types of terrain that you typically traverse through.

We hope this guide will save you some time and money that would’ve been spent paying someone else to do.

There’s a sense of satisfaction that comes with doing something yourself that money can’t buy and it’s even better when this principle involves finding the best bike frame for your needs.

Shailen Vandeyar

A proud Indian origin Kiwi who loves to plant trees and play with my pet bunny when not out cycling through the best routes, reviewing the latest gear, and sharing tips on everything biking.

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