How To Measure Bike Tire Size For Inner Tube

If you’ve been trying to work out how to measure the tire size on your bike for a replacement inner tube, then I’ve got a pretty good idea of how frustrated you’re feeling right now.

It’s something that should be incredibly easy and yet seems to be more like rocket science. But, fear not, I’m here to make life easy for you. I’ve got a couple easy things for you right now. The first is a a table that shows each of the most popular tire sizes along with a recommended inner tube, and a link where you can go straight to an online retailer and buy one for yourself right away. I’ve also got a simple process for you to follow to determine what size your bike tires are. All you need is your bike tire and a sharp pair of eyes – no measuring required!

Take a deep and relaxing breath (it’s going to be easier from now on, I promise) and let’s go have a look.

Recommended inner tubes for popular bike tire sizes

Here you’ll find an easy to follow table showing the most common bicycle tire sizes and a couple recommendations for great inner tubes that fit those tires.

When you’ve determined your tire size – we’ll get to that in a moment – you just click on the bar below that shows your tire diameter (such as “700c”) and this will open up to show the tire widths that are available and buttons to click to see the inner tubes.


27.5 inch tire diameter
26 inch tire diameter
20 inch tire diameter


Recommended tube




16 inch tire diameter


Recommended tube





How to measure your bicycle tire size for a new inner tube

Look up “bike inner tube” on Amazon and you’ll get over a thousand black rubber rings showing up. They all look pretty similar but they’ve got different reference numbers and sizing – so, how do you choose between them?

Well, luckily it’s easy to work out what size your bike tyre is and you can then use that to pick the right size of inner tube.

Here’s what you need to do. First, squat down next to your bike so that you can see the wheel from the side. Now, have a look around the sidewall of the tire – this is the rubber circle that sits in between the metal wheel rim and the tire knobbles that touch the ground. The sidewall is usually black but on some bikes, such as cruisers, it can be tan or white. The color doesn’t matter because what you’re looking for is a series of numbers. You might find a brand name for the tires (such as Schwalbe or Continental) and you’ll also see numbers which look like either of the following:

26×1.5 (an imperial system code)
700c x 23 (a metric system code)

If you see an imperial code, this is the sizing of your tire in inches (e.g. 26” diameter x 1.5” width). A metric code is in millimeters (e.g. 700mm diameter x 23mm width).

The inner tube that you need will have code that includes the tire diameter (from the examples above this would be 26” or 700mm) and a width that includes the tire width (e.g. 1.3”-1.7” or 19-25mm).

To choose the correct size of inner tube, simply take your tire size code and look this up in the table above. Right next to your tire size will be a recommended inner tube and a second alternative (if the first one isn’t available).

What do bike tire codes mean?

Want to delve a little more into what the tire size codes mean? Ok, let’s take a look.

The first number in the code (such as 26 or 700) is the nominal diameter of the tire in either inches or millimeters. This will vary somewhat according to the tire pressure, so it’s not a good idea to try and measure it with a ruler or tape measure. Tires that are under-inflated, or with very worn treads, can have a smaller diameter than the one that’s shown on the tire sidewall.

The second number (e.g. 1.5 or 23) is the nominal width of the tire, again in either inches or millimeters. Again, what you can actually see of the tire width will vary based on how much air the tire has in it, so an actual measurement might well differ from the tire code.

If you see a “c”, for example in “700c x 23” then this refers to an old French system of classifying bike tires according to their widths. An “a” tire was the narrowest and a “d” was the widest. So long as you have the tire diameter and width code numbers, you can safely ignore this letter.

It’s keeping in mind that you shouldn’t swap from tires or tubes measured in inches to ones measured in millimeters. These number codes are nominal, meaning that they don’t necessarily match up to the actual tire and tube dimensions. So, a millimeters tire is unlikely to fit well on an inches wheel and you’ll probably get problems down the road. Stick with imperial tires for imperial wheel rims and vice versa.