How To Measure The Size Of A Bike

kid with bike

It's not like you go to a bike shop and buy one without knowing its measurement. You must measure the bike if you don't want to end up with one that doesn't fit you properly. Buying a bike with an improper size can lead to discomfort, injury, and even poor control issues.

Therefore, it's crucial to know the bike size before getting one. Wondering how to measure the size of a bike? It's not that simple, you have to measure a bike in many different ways to find out the actual size, such as:

  • Seat Tube

  • Top Tube

  • Head Tube

  • Stack, and Reach

  • Chainstay Length, and so on.

These are the key aspects you need to follow while measuring a bike. However, if you don't have rich knowledge about them, stay here. In this article, I will discuss them and explain the importance of considering bike size.

Why Should You Consider The Bike Size?

red and black bike

Whether it's a traditional bike or an electric bike, the size of the bike is really important. The size or measurement is more crucial when you're getting a bike from a reputed online store like samebike.

That is because then you'll have no chance to physically try the bike and see if it fits well or not. Another thing is that bikes come in different sizes, including M, S, XL, and so on, and the sizes will vary based on the manufacturer.

Therefore, when you know the seat tube length, stack, and reach, top tube, head tube measurements, you can easily determine if the bike is right for you. And getting the right bike will not only ensure enough comfort but also your safety and excellent control.

How To Measure The Size Of A Bike

Here is the most important part, which is how to measure the size of a bike. Although different bikes like road, mountain, hybrid, and many others have different sizes, it's better to determine the actual size by yourself.

In the section below, I'll show you how to measure your bike's size while maintaining all the required aspects. Have a look:

Seat Tube Length:

guy showing seat tube length

The first thing you need to do to measure the size of your bike is to measure the seat tube length. And to do so, measure the distance between the seat post clamp and the bottom bracket with the use of a tape measure.

However, this vertical distance or length is also called frame size, which is measured in both inches and centimeters. Here is a chart of the various types of bikes and their frame sizes:

  • Road Bike:

Rider's Height (cm) Insane (cm) Frame Size (cm)
147-160 (cm) 63-73 (cm) 48 cm (XXS)
160-165 (cm) 71-76 (cm) 50 cm (XS)
160-170 (cm) >73-78 cm 52-53 cm (S)
170-175 cm 76-81 cm 54-55 cm (M)
175-180 cm 81-84 cm 56-58 cm (L)
180-188 cm 81-86 cm 58-60 cm (XL)
191-198 cm 88 cm+ 60-63 cm (XXL)

  • Mountain & Hybrid Bike:

Rider's Height (cm) Leg inseam (cm) Frame Size (in)
147-157 cm 61-66 cm 33-35 cm (XS)
157-168 cm 68-76 cm 38-40 cm (S)
168-178 cm 73-78 cm 43-45 cm (M)
178-185 cm 78-84 cm 48-50 cm (L)
185-193 cm 81-90 cm 53-56 cm (XL)
193-198 cm 81-86+ cm 56-61 cm (XXL)

Note: All tables show an approximate frame size that riders can choose based on their height. Before measuring the size of a bike, make sure to find out your height and inseam. Once you know your height and inseam, you can easily find the best-sized bike for you.

Top Tube length:

guy showing top tube length

Take a measuring tape, and measure the distance from the top tube's head tube center to the seat tube center. That horizontal distance is the actual length of a top tube, and this measuring method is applicable for both slope and horizontal top tubes.

However, if you're wondering how to find out the ideal bike's top tube length for you, it's really simple. Get the length of your torso and arms, and then add both numbers together, divide the result by two, and subtract six.

Now you'll have the ideal top tube length in inches, and to convert it to centimeters, simply multiply the result by 2.54. However, for your convenience, I've included different types of bikes' top-tube lengths.

  • Road Bike:

Riders Height Frame Size Top Tube Length
4'11"-5'1" 38 cm (XS) 516 mm
5'2"-5'5" 45 cm (S) 524 mm
5'5"-5'9" 53 cm (M) 536 mm
5'9"-6'1" 56 cm (L) 550 mm
6'1"-6'4" 59 cm (XL) 571 mm
6'4"-6'6" 63 cm (XXL) 592 mm
  • Mountain Bike:

Riders Height Frame Size Top Tube Length
4'11"-5'2" 38 cm (XS) 518.9 mm
5'2"-5'5" 45 cm (S) 518.5 mm
5'5"-5'9" 53 cm (M) 543.3 mm
5'5"-5'9" 56 cm (L) 566.8 mm
6'1"-6'4" 59 cm (XL) 583.4 mm
6'4"-7' 63 cm (XXL) 615 mm

Now you might have a pretty good idea about top tube length and how to find out the ideal top tube length for you.

Head Tube length:

guy showing head tube length

Another essential aspect you need to determine when measuring the size of a bike is the head tube length. You can find out the head tube length by measuring the head tube from bottom to top.

A long head tube will lift the front end of the bike, which will place the rider in an upright position. On the other hand, a short head tube will lower the front side, which offers an aerodynamic position.


Stay updated with our newsletter

Here are different bikes' head tube lengths that you can look at to get some ideas:

  • Road Bike:

Riders Height Frame Size Head Tube Length


38 cm (XS)

110 mm
5'2"-5'5" 45 cm (S) 130 mm
5'5"-5'9" 53 cm (M) 160 mm
5'9"-6'1" 56 cm (L) 180 mm
6'1"-6'4" 59 cm (XL) 205 mm
6'4"-6'6" 63 cm (XXL) 230 mm
  • Mountain Bike:

Riders Height Frame Size Head Tube Length
4'11"-5'2" 38 cm (XS) 110 mm
5'2"-5'5" 45 cm (S) 120 mm
5'5"-5'9" 53 cm (M) 145 mm
5'5"-5'9" 56 cm (L) 160 mm
6'1"-6'4" 59 cm (XL) 175 mm
6'4"-7' 63 cm (XXL) 205 mm

Note:Different manufacturers make a bike differently; therefore, you'll find differences in the frame size or length. Not only conventional bikes but also e-bikes that are powered by quality batteries, like Unit pack power, come in a variety of frame sizes and shapes.

Reach & Stack:

bike showing stack bike showing reach

Last but certainly not least, you need to measure the reach and stack when figuring out the size of a bike. The horizontal distance between the bracket center and the top center of the head tube is measured as reach. On the other hand, the stack is the vertical height of the same points.

Both stack and reach determine how tall and how long the frame is. However, reach describes how far the rider must bend or reach to grasp the handlebars. With a longer reach, you have to bend your back a lot, and for a smaller reach, you have to do the opposite.

When it comes to stack, a higher stack height results in a slightly more upright position while riding. Low stack height, on the other hand, will force the rider to bend their back more than their natural position.


That's it. Now you know pretty much everything about how to measure the size of a bike and what aspects are related to it. In this article, I've discussed four key aspects that you should never miss while measuring the size of a bike.

And the fact is, there are many other aspects that you can look at while determining the actual size of a bike that will suit you. Some of the other aspects are fork rake and offset, chainstay, wheelbase, trail, bottom bracket drop, and so on.

So, no matter if you're getting an old or new bike, always make sure to measure the size so that you don't have to regret it later.

About Author:

image of Kevin Pommells

Hi, I'm Kevin Pommells, a lover of camping and the great outdoors as everyone says nowadays. I'm also a passionate soccer fan and the proud owner of, a website dedicated to helping campers and outdoor enthusiasts make the most of their adventures. With years of experience exploring the wilderness and a deep love for the sport of soccer, I'm always looking for new ways to combine my two passions and share my knowledge with others. Follow me for tips, tricks, and insights on all things camping and outdoor recreation.

Follow Me @ Twitter | Facebook |

As an Amazon Associate I earn from qualifying purchases.

We are a participant in the Amazon Services LLC Associates Program, an affiliate advertising program designed to provide a means for us to earn fees by linking to and affiliated sites.