Free tool
Tyre size checker
Decode any tyre size and its load index and speed rating, and compare two sizes: diameter, sidewall, speedometer error and the 3% rule.
Find your tyre size by reg
Enter your registration number to see the tyre sizes your car left the factory with.
Could not read that size. Try e.g. 225/45R17
It is printed after the size on the sidewall, for example 205/55 R16 91V. You can also type the full code into the size field above.
Maximum speed
km/h / mph
Speed symbol not recognised.
Maximum load
kg per tyre
Load index not recognised.
About kg across a set of four.
The speed rating is the speed the tyre is tested for, not a legal limit. The UK maximum is 70 mph. Replacement tyres should meet or exceed the load index and speed rating in your vehicle handbook.
Diameter difference
Speedometer reads 60 mph, you are doing
- Overall diameter
- mm
- Sidewall height
- mm
- Section width
- mm
- Circumference
- mm
- Revolutions per mile
How tyre sizes work
A tyre size such as 205/55 R16 tells you three things: the tyre is 205 mm wide, its sidewall is 55% of that width tall, and it fits a 16 inch wheel. From those numbers we work out the overall diameter, which decides how far the car travels per wheel revolution.
When you change tyre size, keep the overall diameter within about 3% of the original. Otherwise your speedometer and odometer drift, and ABS, traction control and wheel arch clearance can be affected. Type two sizes above to see the exact difference.
Tyre speed rating chart
The letter after the load index is the speed symbol: the top speed the tyre is built and tested for. In the UK the national speed limit is 70 mph, so ratings are about safety margin and vehicle approval, not permission to go faster.
| Symbol | Max speed (km/h) | Max speed (mph) |
|---|---|---|
| J | 100 | 62 |
| K | 110 | 68 |
| L | 120 | 75 |
| M | 130 | 81 |
| N | 140 | 87 |
| P | 150 | 93 |
| Q | 160 | 99 |
| R | 170 | 106 |
| S | 180 | 112 |
| T | 190 | 118 |
| U | 200 | 124 |
| H | 210 | 130 |
| V | 240 | 149 |
| W | 270 | 168 |
| Y | 300 | 186 |
Tyre load index chart
The number before the speed symbol is the load index, which maps to the maximum weight one tyre can carry. For example, index 91 carries 615 kg per tyre.
Show the full load index table (60 to 120)
| Index | Max load |
|---|---|
| 60 | 250 kg |
| 61 | 257 kg |
| 62 | 265 kg |
| 63 | 272 kg |
| 64 | 280 kg |
| 65 | 290 kg |
| 66 | 300 kg |
| 67 | 307 kg |
| 68 | 315 kg |
| 69 | 325 kg |
| 70 | 335 kg |
| 71 | 345 kg |
| 72 | 355 kg |
| 73 | 365 kg |
| 74 | 375 kg |
| 75 | 387 kg |
| 76 | 400 kg |
| 77 | 412 kg |
| 78 | 425 kg |
| 79 | 437 kg |
| 80 | 450 kg |
| Index | Max load |
|---|---|
| 81 | 462 kg |
| 82 | 475 kg |
| 83 | 487 kg |
| 84 | 500 kg |
| 85 | 515 kg |
| 86 | 530 kg |
| 87 | 545 kg |
| 88 | 560 kg |
| 89 | 580 kg |
| 90 | 600 kg |
| 91 | 615 kg |
| 92 | 630 kg |
| 93 | 650 kg |
| 94 | 670 kg |
| 95 | 690 kg |
| 96 | 710 kg |
| 97 | 730 kg |
| 98 | 750 kg |
| 99 | 775 kg |
| 100 | 800 kg |
| 101 | 825 kg |
| Index | Max load |
|---|---|
| 102 | 850 kg |
| 103 | 875 kg |
| 104 | 900 kg |
| 105 | 925 kg |
| 106 | 950 kg |
| 107 | 975 kg |
| 108 | 1,000 kg |
| 109 | 1,030 kg |
| 110 | 1,060 kg |
| 111 | 1,090 kg |
| 112 | 1,120 kg |
| 113 | 1,150 kg |
| 114 | 1,180 kg |
| 115 | 1,215 kg |
| 116 | 1,250 kg |
| 117 | 1,285 kg |
| 118 | 1,320 kg |
| 119 | 1,360 kg |
| 120 | 1,400 kg |
Popular tyre sizes
- 155/65 R14
- 165/65 R14
- 165/70 R14
- 175/65 R14
- 175/65 R15
- 185/60 R15
- 185/65 R15
- 195/50 R15
- 195/55 R15
- 195/60 R15
- 195/65 R15
- 205/55 R16
- 205/60 R16
- 195/55 R16
- 195/65 R16
- 205/50 R16
- 215/55 R16
- 215/60 R16
- 225/50 R16
- 205/45 R17
- 205/50 R17
- 215/45 R17
- 215/50 R17
- 215/55 R17
- 225/45 R17
- 225/50 R17
- 225/55 R17
- 235/45 R17
- 215/45 R18
- 225/40 R18
- 225/45 R18
- 235/40 R18
- 235/45 R18
- 235/55 R18
- 245/40 R18
- 225/40 R19
- 235/40 R19
- 235/50 R19
- 245/40 R19
- 255/40 R19
Frequently asked questions
How do I read a tyre size such as 205/55 R16?
The first number (205) is the tyre width in millimetres. The second (55) is the aspect ratio: the sidewall height as a percentage of the width. R means radial construction, and the last number (16) is the wheel rim diameter in inches. Together they give the tyre its overall diameter.
What is the 3% rule for changing tyre size?
As a guideline, a replacement tyre should have an overall diameter within about 3% of the original. Beyond that your speedometer and odometer become noticeably inaccurate, and ABS, traction control and wheel arch clearance can be affected.
How do I calculate the overall diameter of a tyre?
Multiply the width by the aspect ratio and divide by 100 to get the sidewall height in millimetres. Double it, then add the rim diameter converted to millimetres (inches multiplied by 25.4). For 205/55 R16 that is 2 x 112.75 + 406.4 = 631.9 mm.
Will a different tyre size change my speedometer reading?
Yes. A larger overall diameter covers more road per revolution, so your speedometer reads lower than your true speed. A smaller diameter makes it read higher. Use the comparison tool to see what a speedo reading of 60 mph would really be.
What do the letters and numbers after the tyre size mean, such as 91V?
The number is the load index: 91 means each tyre can carry up to 615 kg. The letter is the speed rating: V means the tyre is rated up to 240 km/h (149 mph). Both are printed after the size on the sidewall, for example 205/55 R16 91V.
What is the maximum speed for each tyre speed rating?
Common ratings are Q 160 km/h (99 mph), S 180 km/h (112 mph), T 190 km/h (118 mph), H 210 km/h (130 mph), V 240 km/h (149 mph), W 270 km/h (168 mph) and Y 300 km/h (186 mph). See the full chart on this page.
Can I fit tyres with a lower speed rating or load index than the originals?
As a rule you should fit tyres that meet or exceed the load index and speed rating your vehicle manufacturer specifies in the handbook or on the door-frame sticker. Lower ratings can compromise safety and may affect your insurance, so ask a tyre fitter if you are unsure.
Where do I find my tyre size?
It is printed on the sidewall of your tyre, usually in the format 205/55 R16 followed by the load index and speed rating. It is also in your vehicle handbook and often on a sticker in the driver door frame or fuel filler flap.
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