How To Find Your Tyre Size

This is a question we get asked a lot and something that’s useful for all drivers to know. All our branches will be happy to check your tyre size for you but if you’re looking for an online tyre quote, all the information you need can be found on the sidewall of your tyre.

Whilst there are online tools that promise to find your tyre size using your registration number details, these can often bring up a choice of sizes and if you’re looking to Click & Reserve your tyres you may end up reserving the wrong size. Knowing exactly where to find the precise size is always the best and most accurate way.

Top Tip: If you have a smart phone then take a quick photograph of the numbers on the side wall of your tyre. Then you’ll always have your tyre size to hand – when you’ve learnt how to crack the code!

What information do I need?

The main information you’re looking for is your tyre size. This consists of the tyre width, aspect ratio and wheel diameter. You will also need to know your load rating and speed rating when looking for a tyre that’s suitable for your vehicle. It’s sounds complicated we know, but once you know what you’re looking for it’s easy!

Take a look on your tyre sidewall, what you’re looking for is a 7 digit number with an R after the first 5 digits. Something like 175/65R14 82T, 205/55R16 91W, 225/45R17 94W or 225/40R18 92Y – there are literally dozens of combinations.

Some vehicles such as BMWs, Mercedes and even Smart Cars have larger sized tyres on the rear so it’s always worth checking both sizes.

The example we’ll use is a very popular tyre size, 205/55R16 91V


205/55R16 91V

The first 3 digits of the tyre size give the measurement for the width of the tyre in mm. So a 205 width tyre will measure exactly 205mm across the tread from from sidewall to the other.

Aspect Ratio

205/55R16 91V

The next pair of number give the measurement for the height of the tyre as a percentage of the tyre width. In this case, the aspect ratio is 55 which means that the height of the tyre is 55% of the tyre width.


205/55R16 91V

The vast majority of tyres manufactured today are “Radial” tyres which is what the letter R refers to.


205/55R16 91V

The last 2 numbers found after the ‘R’ show the size of the wheel rim on the vehicle. In this case, the tyre marked with ‘16’ tells us that the wheel it fits on to is 16” in diameter.