The markings on your tyre’s sidewall can look like a random jumble of letters and numbers. But each one has a specific meaning. They tell you everything from the tyre’s width and construction to its load capacity and speed rating.

Some of these details are only useful to manufacturers, but others are essential for drivers. Understanding your tyre size (and type) matters for safety, fuel economy, handling, and MOT readiness.

Most drivers never check their tyre numbers, let alone understand them. But it can save you time and money. By the end of this article, you’ll know exactly how to read and check tyre markings confidently and correctly.

Where to Find Your Tyre Size

The first step is finding the tyre markings, also known as tyre numbers. They’re usually printed on the sidewall and follow a standard format of numbers and letters used worldwide.

Look for something like this: 205/55 R16 91V.

But that’s not the only place to inspect. You’ll find the information printed on the door frame or the fuel filler cap, detailing tyre details and pressures. You can also check your car’s handbook.

Remember to check all your tyres. They’re not always the same. Tyre size must match across each axle for safety and legality; otherwise, it can cause serious problems with your vehicle.

What the Numbers on Your Tyre Mean

You don’t need to be a codebreaker to decipher the tyre numbers. Once you understand the format, it’s quite simple.

Let’s take our previous example: 205/55 R16 91V.

Here’s a breakdown:

• 205 – Tyre width in millimetres (the distance from one sidewall to the other).
• 55 – Aspect ratio (sidewall height as a percentage of the tyre width, in this case 55% of 205mm).
• R – Radial construction (the standard type used in almost all modern tyres).
• 16 – Rim diameter in inches (the wheel size the tyre fits).
• 91 – Load index (indicates the maximum weight each tyre can carry here)
• V – Speed rating (the maximum speed the tyre can safely handle)

You can see below further details on what the tyre numbers mean for our example: 205/55 R16 91V, or you can find more information here on Load Index and Speed Rating.

UK Tyre Size and Markings Chart

How to Choose the Right Tyre Sizes for Your Car

Always trust an expert to select the right tyre sizes for your vehicle. The manufacturer will recommend a particular size, listed in the manual or door sticker. It’s sensible to follow the recommendation.

Why? Well, incorrectly sized tyres are an automatic MOT failure. But even practically, incorrectly sized tyres often lead to uneven wear and fuel inefficiency. In the worst cases, it can damage the vehicle itself, affecting the suspension and ride.

There are a few exceptions:

• Winter or all-season tyres might require slightly narrower tyres for better grip on snow or ice.
• Performance tyres might require wider or lower-profile tyres to improve handling or aesthetics.

Just make sure any change stays within your manufacturer’s approved specifications.

Common Tyre Markings Explained

Tyre numbers aren’t the only markings on a tyre. Besides the main size code (e.g., 205/55 R16 91V), there are other markings on a tyre’s sidewall to understand. These markings aren’t about size. They give extra information about performance, strength, or age.

These tyre markings include:

• DOT code. The last four digits show the manufacturer date, e.g., 2419 means week 24 of 2019. Tyres should be inspected after 5 years and ideally replaced by 10, even if the tread looks fine.
• M+S and 3PMSF mean mud and snow or three-peak mountain snowflake. The tyre has passed official winter-performance tests.
• XL / RF means extra load or reinforced. Tyres built to carry heavier loads, e.g., for vans or SUVs.
• Run-flat (ROF, EMT, EFT, ZP, SSR, or DSST) are specialist tyres that continue to function despite a loss of pressure or puncture.

How to Check Tyre Size During Replacement

Planning on getting a new set of tyres? Here are a few tips:

• Always read the size directly from the current tyre sidewall before ordering or fitting.
• Compare it with the size listed in your vehicle handbook or door frame sticker.
• Check all four tyres; some cars have different sizes on front and rear axles.

Enter your registration or car model to look up your tyre size via our website. That can help narrow down which tyres in our selection are right for your vehicle. Just double-check that the marking matches the ones listed in the vehicle handbook.

If you’re unsure, our technicians can confirm the right fit and handle installation safely.