How To Read Your Tyre Size

How do I find my tyre size?

How do I find my tyre size?

You will find your tyre size on the side of your current tyres. Tyre sidewalls contain a lot of information, but the size is usually quite prominent, in some of the biggest writing.

It consists of three key numbers; for example, 205/55 R16. Another few characters follow the size, like 91V on our example tyre.

What do the numbers mean?

The size breaks down into three numbers. Using our example size, 205/55 R16, this is what each number means:

205 is the width of the tyre tread in millimetres. This goes up in increments of 5. WhatTyre’s Search By Tyre Size function allows you to select widths between 165 and 305.



55 refers to the profile of the tyre, or the distance between the wheel and the edge of the tyre, looking at it from the side. The number is the percentage of the width of the tyre. It is commonly known as the “aspect ratio”. So, the profile of our example tyre is 55% of 205mm, or 112.75mm. This number also increases in increments of 5.


16 is the rim size, or the diameter of the inside of the tyre. It is expressed in inches and increases in increments of 1. WhatTyre’s Search By Tyre Size function currently allows you to search for tyres with rim sizes from 13 to 24.


Why is there an R in there?

The letter R means “radial” which is the way the tyre is constructed.

What do the numbers and letter after the tyre size mean?

Congratulations! You are officially interested in tyres.

These figures show the limits of how you can use the tyre. The number is the “load index”, or how much weight the tyre can carry.

speed rating iconThe letter is the speed rating. This tells you the maximum speed the tyre is suitable for. This is the fourth and final part of your WhatTyre tyre search. Most car tyres for road use have a maximum speed between 118mph (T) and 187mph (Y).

Therefore, our example tyre has a maximum speed of 150mph as it has the speed rating V. The load index of 91 means it can carry a load of 615kg.

Why can’t I just put my car reg number in?

WhatTyre wants to promote tyre knowledge in the wider car tyre market. We think everyone should be able to find and understand their tyre size.

While it is possible to use your car registration to find your tyre size, this is unreliable and could result in you spending a lot of money on the wrong size tyre. Many such searches will still ask you to identify your tyre size from a number of options anyway. We think it is better to know for sure that you are buying the correct size tyre.

If we can help you with anything else, you can contact WhatTyre on any of our social media channels.