Key takeaways
- Your tyre size is written on the sidewall of your current tyres, for example 205/55 R16 91V, and on the placard inside the driver's door.
- Read it in order: width in millimetres, profile percentage, rim diameter in inches, then the load index and speed rating.
- Always match the load index and speed rating your vehicle requires, never a lower one, as fitting below spec can affect handling and insurance.
- Some cars run different sizes front and rear, so check every wheel rather than assuming all four match.
Buying tyres is simple once you know your size, and your car tells you in two places. The trouble is the markings look like a random code. This guide shows you exactly where to find your tyre size, how to read every part of it, and the few situations where the size is not the same on all four corners.
How do you find the right tyre size for your car?
You find your tyre size in two reliable places: moulded into the sidewall of your existing tyres, and on the placard inside the driver's door shut. Both list a code such as 205/55 R16 91V. Match that code exactly when you buy, and the new tyres will fit your wheels and suit your car.
The sidewall tells you what is fitted now, while the door placard tells you what the manufacturer originally specified. Usually they agree. If they differ, it may mean a previous owner changed size, so it is worth understanding both before you order.
Where is your tyre size listed?
Your tyre size appears on the tyre sidewall and on the vehicle's tyre placard. The placard is a small sticker inside the driver's door frame, sometimes on the fuel filler flap or in the handbook. It gives the size plus the recommended pressures, so it is the single most useful label on the car.
Reading the size off the tyre itself is just as valid, as long as the tyres currently fitted are the correct ones. If you have any doubt that the right size is on the car, trust the door placard. It reflects what the manufacturer designed the car around.
How do you read the tyre size code?
The code reads in a fixed order, and each part means one thing. Take 205/55 R16 91V as the example. The 205 is the width, the 55 is the profile, the R16 is the construction and rim, and the 91V is the load and speed. Decode them left to right and nothing is left to guess.
Width and profile
The first number is the tyre width in millimetres, so 205 means 205mm across the tread. The second number is the profile, the sidewall height as a percentage of the width. A 55 means the sidewall is 55% of 205mm. Lower profiles look sportier and sharpen steering; higher profiles cushion the ride.
Rim diameter
The R stands for radial, the construction used by almost every modern car tyre. The number after it is the wheel rim diameter in inches, so R16 fits a 16-inch wheel. This figure must match your wheels exactly. A tyre built for a different rim size simply will not seat on your wheel.
Load index and speed rating
The last pair is the load index and speed rating. The number, here 91, is a code for the maximum weight the tyre can carry. The letter, here V, is the maximum speed it is rated for. Fit tyres that meet or exceed the figures your vehicle requires, never below them.
Our full guide on what the numbers on your tyre mean breaks every marking down further, including the DOT date code and winter symbols.
| Part of 205/55 R16 91V | What it means |
|---|---|
| 205 | Tread width in millimetres |
| 55 | Profile: sidewall height as % of width |
| R | Radial construction |
| 16 | Wheel rim diameter in inches |
| 91 | Load index (maximum weight code) |
| V | Speed rating (maximum rated speed) |
Can you fit a different tyre size?
You should normally fit the same size your car was designed for. Some approved alternative sizes exist, but the rim diameter must always match your wheels, and any change must keep the correct load and speed ratings. Changing width or profile alters the rolling circumference, which can affect the speedometer, handling and even the ABS.
If you want to move away from the original size, check it against the manufacturer's approved options rather than guessing. The safest route is to match the door placard, which removes all doubt and keeps everything calibrated as intended.
Why might your four tyres show different sizes?
Some cars, especially performance and rear-wheel-drive models, are designed with wider tyres on the rear axle than the front. This is called a staggered fitment, and it is deliberate. On those cars you cannot simply read one tyre and order four the same, so always check every wheel before you buy.
On most ordinary cars all four are the same size. But a previous repair or a fitted spare can leave an odd one out, so a quick walk around the car takes seconds and avoids ordering the wrong tyre. Knowing whether to replace in pairs or as a full set also helps. See our guide on whether to replace two or all four tyres.
Getting the right size fitted
Once you have your size, ordering is the easy part. Match the width, profile, rim, load index and speed rating, and the tyre will fit. If you would rather not measure, fit or carry tyres yourself, Fast Tyre confirms your size and brings the correct tyres to you. Our mobile tyre fitting service comes to your home, work or the roadside across London and central England, usually within 30 to 60 minutes, and fits them on the spot.
Frequently asked questions
In two places: moulded into the sidewall of your current tyres, and on the placard inside the driver's door shut, fuel flap or handbook. Both show a code such as 205/55 R16 91V. Match it exactly when buying replacements and the tyres will fit your wheels.
Reading 205/55 R16 91V: 205 is the width in millimetres, 55 is the profile as a percentage of width, R is radial, 16 is the rim diameter in inches, 91 is the load index, and V is the speed rating. Together they define the exact tyre your car needs.
Usually you should match the original size. Some approved alternatives exist, but the rim diameter must match your wheels and the load and speed ratings must be met. Changing size affects the speedometer and handling, so stick to the door placard unless a fitter confirms a safe alternative.
Some performance and rear-wheel-drive cars use a staggered fitment, with wider rear tyres by design. That is normal. Always check every wheel rather than assuming all four match, as a previous repair or a fitted spare can also leave one tyre a different size.
You must fit at least the speed and load ratings your vehicle requires, and never lower. You can fit a higher rating safely. A lower rating than specified can affect handling and may invalidate your insurance, so check the placard figure before buying budget options.