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How to Measure a Mountain Bike Frame Properly & Accurately

Written by Gary Johnson / Fact checked by Henry Speciale

how to measure a mountain bike frame

Before deciding to buy a bike, it’s important to know your body measurements and the type of riding you intend. You have to make sure that the money you spend on it is worthwhile.

If a bike doesn’t fit, it will be uncomfortable and not work well for the type of biking you want. These are significant factors to evaluate before purchasing your dream ride.

In this article, you will properly learn how to measure a mountain bike frame that fits you perfectly.

What You Need to Prepare

In measuring mountain bike frame, these are the three tools you need.

  • Spirit Lever
  • Tape Measure
  • Ruler

How to Correctly Measure a Bike Frame Length


1. Seat Tube Length

Measure the seat tube length starting from the distance between the center of the crank and the joint where it attaches to the seat tube.

This length, along with top tube length, drives your bike size. Please note that a bike frame with suspension will also affect its height.

2. Top tube length

The length of the top tube is its distance from the seat tube center to the head tube center. Measure the length by placing the tape measure at the center points.

Use and extend measuring tape so the joint of the top tube will join the seat tube joint. You can record the measurements in centimeters or inches.

3. Head tube length

The head tube length is the distance between the joint at the top of the head tube and where it meets the fork. It’ll tell you how high your bike’s front axle is from a given point on its frame if you measure this.

4. Top Tube and Seat Tube Slope

For this bike frame measurement, you will need the spirit lever and a tape measure.

  • Place your front and back wheels at the same level.
  • Using the spirit lever, draw a line straight down from the joint at the head tube to the front fork. The length of this line should be your steering pivot point, and it will guide you on where to drill for mounting points on your bike.
  • Mark the point where the line intersects the tube.

Finally, use a ruler to measure the distance between the head tube hole and front fork joint, and mark this on your post.

How to Determine Your Bike Size


You’ll need to figure out what type of bike you require. You should also consider how you intend to use your bike and which are the important features. Once you’ve determined the purpose of your bike, you may start measuring your frame size.

  • Height

A comparison of a bike frame to your height is one of the simplest methods, but it won’t always produce a perfect fit. Instead, it’s only an acceptable method for determining whether or not the frame size for adults is too short or too tall.

It is important to note that road and mountain bikes have different sizing standards. Womens sizes follow the same guide as well for mens. Check out this mountain bike frame size chart.

Your leg and your arm length are significant contributing factors to cycling. Even though you might be a certain height, your legs may have an incompatible inseam length.

  • Mountain Bike Size Chart
Rider Height(in) Frame Size(in) Bike Size
4’10” – 5’2” 13″ – 14″ X-Small
5’2″ – 5’6″ 15″ – 16″ Small
5’6″ – 5′ 10″ 17″ – 18″ Medium
5’10” – 6’1″ 19″ – 20″ Large
6’1″ – 6’4″ 21″ – 22″ X-Large
6’4″ – 6’6″ 23″ – 24″ XX-Large

If we take a look at the chart, a 27.5 inch will still fall under an XL frame MTB. Meanwhile, 17 inch bikes are for medium sizes and 19 inch bikes are for large ones. and a 21 inch bike falls under X-Large size.

  • Bike Fit

Provide your measurements and preferences to ask for help from a bike fit expert to assist you through the process. That ensures that you receive the appropriate size and a bike that meets your unique demands.

The bike fit will also provide you with more intricate measurements. This can be quite beneficial for beginner cyclists and athletes.

  • Mountain Bike Suspension

A bike frame with suspension allows you to ride on rough and rocky terrains with ease acting as the bike’s shock absorber. It helps keep your tire on the ground, especially when going downhill at high speed.

If you are riding a mountain bike with a lower height, the suspension will lower your seating height when bouncing on rocky surfaces. You may try getting a height 2 inches higher to provide an allowance for the bike suspension.


The best way to get your frame size is to test ride the bike and try to feel its comfort while sitting on it. It will make the process much easier, and you’ll be well-equipped from the start.

Now that you know how to measure a mountain bike frame, you will definitely arrive at the best decision for your bike purchase and improve your cycling experience in every aspect.

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