How to read tire size
Type the code from your tire’s sidewall and see what every part means, from the width to the load index and speed rating.
- P · Tire type
- P-metric: passenger car tire (US standard)
- 225 · Width
- 225 mm (8.9 in) from sidewall to sidewall
- 45 · Aspect ratio
- Sidewall height is 45% of the width: 101 mm (4.0 in)
- R · Construction
- Radial: cords run across the tire. Almost every modern tire.
- 17 · Wheel diameter
- Fits a 17-inch wheel
- 94 · Load index
- Up to 1,477 lb per tire (670 kg)
- W · Speed rating
- Up to 168 mph sustained
Overall diameter: 25.0 inches · 808 revolutions per mile · compare with another size
Tire size meaning, part by part
A full tire size like P225/45R17 94W has seven parts:
| Part | Example | Meaning |
|---|---|---|
| Tire type | P | Passenger (P), light truck (LT), trailer (ST), temporary spare (T). No letter: Euro-metric. |
| Width | 225 | Section width in millimeters. |
| Aspect ratio | 45 | Sidewall height as a percentage of the width. |
| Construction | R | Radial. A Z before it (ZR) is an older high-speed marking. |
| Wheel diameter | 17 | The wheel size in inches. |
| Load index | 94 | Maximum load per tire: 94 = 1,477 lb. |
| Speed rating | W | Maximum sustained speed: W = 168 mph. |
Tire speed ratings
| Rating | Max speed | Typical use |
|---|---|---|
| Q | 99 mph | Winter tires |
| R | 106 mph | Light trucks, all-terrain |
| S | 112 mph | Light trucks, all-terrain |
| T | 118 mph | Family sedans and minivans |
| H | 130 mph | Most passenger cars |
| V | 149 mph | Sport sedans |
| W | 168 mph | Performance and sports cars |
| Y | 186 mph | Performance and sports cars |
How to check your tire size
- Look at the sidewall of any tire: the size is the largest code, starting with a number or with P or LT.
- Compare it with the placard on the driver’s door jamb. That shows the size your car was built for, and the right tire pressure.
- If the two differ, the tires were changed. Check the difference with the tire size calculator.
Want the size in inches? Every common size is listed in the tire size chart.
Questions
Where do I find my tire size?
On the tire's sidewall, in raised letters like P225/45R17 94W. Your car's recommended size is also on the placard inside the driver's door jamb and in the owner's manual.
What does 225/45R17 mean?
225 is the tire's width in millimeters, 45 means the sidewall is 45% as tall as the tire is wide, R means radial construction, and 17 is the wheel diameter in inches.
What do the numbers after the size mean, like 94W?
94 is the load index: each tire can carry up to 1,477 lb. W is the speed rating: it's built for up to 168 mph sustained. Replacement tires should match or exceed both.
What does the P or LT at the start mean?
P means a P-metric passenger tire. LT is a light-truck tire with a stronger construction for heavy loads and towing. No letter means a Euro-metric tire, which is also fine for passenger cars.
How do I read a tire's age?
Look for the DOT code: the last four digits are the week and year it was made. 2724 means the 27th week of 2024. Many makers recommend replacing tires after 6 to 10 years regardless of tread.
