Inner Tube Size Guide

ULTIMATE Inner Tube Size Guide

Whether you've got a puncture or are in need of a spare; getting the right inner tube is paramount. Our inner tube size guide is the quick way to understand what you need and get it right first time. Knowing what bike inner tube size you need really is one of cyclings fundamentals. No matter if you've a road bike, mountain bike or BMX it's all the same. Once you know your tube sizes; you've got it for life, so grab a brew and have a read.  


Bike tyre side wall showing bike tyre sizes


DO Look on the side of the tyre(s) you wish to replace the tube of and find the specification. Be sure to check both front and rear tyre(s) if applicable as many bikes use a combination of sizes. Once you've found all the numbers on your bike tyre, it's time to understand them. In our example it reads 44-559 (26 x 1.95).

DO NOT use the size on the inner tube, always use the tyre specification on the side wall of the tyre. It's mainly because the tube inside the tyre may not actually be the right size (especially with second hand bikes). So, you'd be replacing the wrong tube again. Also, manufacturers can use a tube with limited size range (because it's cheaper) which then would limit your options of which other tubes you could use. So always get your inner tube size from your bike tyre! 


ETRTO Tyre Sizing and Imperial Tyre Sizing

2. ETRTO or Imperial Sizing

On the tyre wall are usually two sets of numbers. Traditionally, English or Imperial Sizing has been used to find inner tube and tyre sizes. However, the best inner tube sizing method is done by using ETRTO sizing. ETRTO is an International Sizing Standard making it clear and simple to understand. For those who are interested it means European Tyre and Rim Technical Organisation. In our example we have both sizing versions. Other common conversions of Imperial to ETRTO sizing are below:


507 = 20" BMX Wheel Diameter (Example: 20 x 2.125)
406 = 20" Commuter (Brompton) Bike Diameter (Example: 20 x 1 3/8)
349 = 16" Vintage folding bikes (Example 16 x 1 3/8)
305 = 16" Kids Bikes (Example: 16 x 1.95)
559 = 26" Mountain Bike (Example: 26 x 2.125)
584 = 27.5" Mountain Bikes (Example: 
622 = 29" Mountain Bikes
622 = 700c Road Bikes (700 x 25)


Bike Tyre wall Sizing and Specification



To determine the tyre size, there are 2 number required (using either ETRTO or Imperial sizing). One will be the diameter of the tyre, the other will be the width of the tyre. In this example we have 44-559 (ETRTO size) and 26 x 1.95 (imperial size). You need both numbers. Below are some popular sizes and their examples.

  • Children's Bike Inner Tube size example:

1. Diameter - 12" to 18" 
2. Widths - 1.75 - 2.125

  • BMX Inner Tube size example:
1. Diameter - 20"
2. Width - 1.75 - 2.40


  • MTB Inner Tube size example: 

1. Diameter - 26" to 29"
2. Width - 1.95 - 3.50


Inner Tube Size Example


3. Inner Tube Size Examples

Now we can determine what we are looking for in an inner tube. So if we use 26 x 1.95, we need a 26 inch diameter with a 1.95 inch width. Or we can also look for a 559 diameter and a 44 width. Knowing the size information we just need to check the valve type then we are ready to find the right inner tube.



Valve type examples

4. Valve Type

You must replace the valve with the same valve type as originally used. Most bikes in the UK will use a Schrader or Presta valve. It really is as important to understand sizing as well as valve types, so do take the time to make sure you know which valve you need. Our complete guide to valve types will help.

Schrader - The Schrader valve is usually standard in size and all will likely be compatible. But if your Schrader valve is over 40mm you will likely need an XL size.

Presta - The presta valve comes in a variety of lengths so you need to measure it. For the majority of bikes, they will use a standard length, usually around 40mm (32mm to 45mm). But for deeper section rims, 50mm, 60mm, 80mm valve lengths are available. 

For full information on inner tube valve types check out our complete guide. In our example we are going to use a Schrader valve (both threaded and un-threaded fit the same). Again our full inner tube valve type guide will give you all the answers.



Inner Tube Box Size Example

4. Putting it all together with an inner tube box Example

Looking at this inner tube box we can see a plethora of information. But if we break it down we can find the sizes we want. We need 26 x 1.95. As you can see it matches 26" but there is no reference to 1.95? Not to worry. Because inner tubes dilate (fancy way of saying stretches) across a range of sizes, 1.95 is in-between 1.75 and 2.00. So this will work.

The same goes for the ETRTO sizing. We can see that 44 is in-between 40 and 47 so it'll fit. The inner tube box doesn't have the space to list every size, so it just gives some examples. As you can see with a bit of logic this tube matches our size. Plus you can see an image of the Schrader valve. So all in all press that buy button!



1. LOOK AT the tyre Sidewall.

2. FIND the ETRTO or Imperial sizing.

3. IDENTIFY the tyre's diameter and width.

4. IDENTIFY what valve type you require (including length).

5. COMPARE what you need with the product you're about to buy.

6. REMEMBER to buy an extra tube as a spare.


If you've any questions or are unsure what you need, please contact us, we're more than happy to help you get the right inner tube.


Bike Tube Size Guide

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