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Tyre sidewall displaying size markings including aspect ratio

Tyre Aspect Ratio - What Does This Mean? How To Measure It?

Do you know what aspect ratio signifies?

Knowing how to read tyre sizes is essential for anyone looking to purchase a new set of rubber, and aspect ratio plays a crucial role in understanding the relationship between a tyre’s width and its height.

Let’s explore more about aspect ratio and how it can directly impact your driving experience.

What Is Tyre Aspect Ratio?

Tyre aspect ratio is a number that represents the height of the tyre’s sidewall in relation to its width.

It is typically expressed as a percentage and can be found following the tyre’s size designation.

For example, if you come across a tyre labelled “225/50R17,” the aspect ratio is 50%.

What Does The Aspect Ratio Of A Tyre Mean?

The aspect ratio of a tyre determines its performance characteristics.

Tyres with lower aspect ratios, commonly known as low-profile tyres, have shorter sidewalls, resulting in improved handling and cornering stability.

They offer a sportier look and better steering response, making them popular among performance-oriented vehicles.

On the other hand, tyres with higher aspect ratios have taller sidewalls, providing a more comfortable ride and better shock absorption on uneven surfaces.

They are commonly found on sedans and SUVs, where comfort and ride quality are prioritised over sporty handling.

How To Measure Sidewall Height From Aspect Ratio

To measure the sidewall height from the aspect ratio accurately, follow these simple steps:

Step 1: Identify The Aspect Ratio Number

Look for the number following the tyre’s width measurement on the sidewall.

For instance, if the tyre width is 205mm, and the aspect ratio number is 55, the aspect ratio is 55%.

Step 2: Calculate The Height

To find the sidewall’s height, multiply the tyre width by the aspect ratio percentage.

For example, with a tyre width of 205mm and an aspect ratio of 55%, the sidewall’s height would be 0.55 x 205mm = 112.75mm.


Choosing the right tyres for your vehicle includes understanding tyre aspect ratio.

So, the next time you’re in the market for new tyres, you’ll be equipped with the knowledge to make the best choice for your driving needs.

Louis from Tyre Geek


I'm Louis, an engineer passionate about helping Australians choose better tyres for their vehicles!