How to determine the tire size for your bicycle

There are many different tire sizes for bicycles, but that's not all – there are also different size systems. With this blog article, we want to provide you with a quick and easy overview and help you find the right size for your bicycle. 

In addition to various tips for choosing the right tires, you will also find a clear table of bicycle tire sizes in all common size specifications here.

What size systems are there?

Bicycle tires (or “covers”) are divided into different size systems:

• In inches
• There are also the ETRTO values
• And the French size specifications.

For a better overview of tire sizes, we have created a table where you can find the different specifications. It is important to know that inches refer to the diameter of the tire, French sizes and ETRTO specifications directly indicate the combination of diameter and width.

Note, in addition to the tire size, the selection of the appropriate tire width also plays an important role! You can find more about this in our article "Find the right tire width for your bicycle".

In our table, you will also find the recommendations for the combinations of tire width and rim width (“rim width” of the rim) listed, which you need if you want to buy new tires for your bicycle that are wider or narrower than the existing ones.

Important: You can find the size of your bicycle tires on the sidewall of the tire (there's a picture below).

Table: Overview of common bicycle tire sizes

The common tire sizes on bicycles in inches

Tire sizes on bicycles are often given in inches . Especially with manufacturers from the USA, you will also find the English term Inch. Especially with mountain bikes, children's bicycles, trekking bikes, and many city bikes, the wheels are measured in inches or Inch.

• Inches is a common size for MTBs, children's bicycles, trekking bikes, and city bikes
• Inch is the English term for inches
• Inches can be abbreviated with “, for example, you will often come across terms like 26” bicycle in product descriptions.
• Note! A 24-inch bicycle has 24” wheels, but the size is used in this case to represent the entire bike!

The following common sizes are usually found in inches:

12 - 24" Inches

These tire sizes mainly appear on children's bikes and balance bikes. Occasionally, they can also be found on folding bikes or recumbent bikes. Compact bikes often have 20”, which also applies to compact e-bikes.

26" Inches

This size was for a long time the common size in the MTB sector and is still occasionally available today. You often find them especially on bikes for teenagers. Additionally, 26” marks the transition from children's bikes to adult bikes.

27.5" Inches

27.5” tires have largely replaced the old 26” tire standard in the enduro, all-mountain, trail, freeride, and downhill sectors. 27.5-inch wheels skillfully balance propulsion and playful handling.

28" Inches

For city, trekking, and touring bikes, 28-inch large bicycle tires are the standard. Similarly, road bikes and gravel bikes are mostly equipped with them (but are not measured in inches).

29" Inches

These tires are mainly found in the marathon and XC sectors, and they are increasingly seen on enduro and all-mountain bikes. Due to their large circumference, they roll significantly better over obstacles, but in return, they are not quite as playful as smaller tires. Occasionally, this tire size can now also be found on downhill bikes.

Here you can also read the manufacturer-recommended air pressure (PSI indication) alongside the size of the bicycle tire.

Bicycle Tire Size Classification According to ETRTO

In addition to the usual size indication in inches, the size classification according to ETRTO (=European Tire and Rim Technical Organization) is still used. Here, the tire width followed by the tire inner diameter – each in millimeters – is specified. The tire inner diameter also indicates the nominal diameter of the rim on which the tire can be mounted. So, if you have a tire with the ETRTO size 37-559, it is 37 mm wide and has an inner diameter of 559 mm. The rim must also have a diameter of 559 mm.

ETRTO and the Rim Width

There are also recommendations for combinations of tire width and rim width. The width of the rim – also called rim width – determines which tire width can be mounted.

A tire that does not fit the rim can, in the worst case, lead to damage and unfavorable riding behavior.

• For example, an extremely wide tire should not be mounted on a very narrow rim.
• Likewise, no tire can be mounted that is too narrow or even narrower than the rim itself.

French Tire Sizes

Another size classification for bicycle tires is the French designation.

Primarily, road bike tires have French sizes, but these tire sizes are also specified for some gravel bikes. An example would be the size 700 x 35C. Here, the three-digit number indicates the approximate outer diameter of the tire, the two-digit number indicates the tire width, and the letter stands for the tire's inner diameter or the rim diameter. At first, this may seem a bit complicated, but a look at our table shows you the actual size of the tire.

Besides the tire size and width, the tire profile significantly influences a bike's riding behavior!

Finding the right tire size... here's how to proceed

Finding the right bicycle tire is not that difficult. 

With a bit of luck, you will find a size and rim width specification on the rim; here 26 inches and 25mm. Then you can easily buy the right tires. Image © DT Swiss

Option 1: 

• If you simply want to replace a worn-out tire, you can look for the size on the sidewall of the old tire and order a new tire in the same size.

Option 2:

• If you would like to test slightly wider or narrower tires, you should know the rim width of your rims. Our table will then help you select the possible tire widths.
• Additionally, you need to know how much tire width your bike frame allows. 
• You can then choose the right tire for your bike from different tire widths in the appropriate diameter.

🔺Buy the right bicycle tires🔺

Wire tires | Tubeless tires | Tube tires | Spike tires | Children's tires

You can find much more information in the other parts of our tire series:

1. Find the right tire width for your bicycle
2. How to convert your MTB to tubeless
3. Everything you need to know about bicycle valves
4. Gravel tires – what you should know!
5. E-bike tires – useful or unnecessary?