Tire Size Explained (What do the Numbers Mean?)

tire size explained

Buying new tires seems like an easy task until you call your workshop, and they ask you what kind of tires you want. This is when you realize that you need to give them some numbers. But what do all the numbers on the tire mean?

tire size explained

Tire Size Meaning

The best way to learn something is by looking at an example. We will take the example of the tire size of the picture above.

We want to buy new tires for our car, and we find this number combination on our tires: “P 225 / 55 R 15 95 H“. But what do they mean? Here is the explanation of this number combination.

  • Letter P: The first letter at the beginning tells us which type of tire we have. In this case, we have a “P”, which means that it is a Passenger car tire. This means that it is made to a certain standard in the USA. You can also find the letters “LT” which means that they are designed for light trucks. If you find no number at all here, it means that the tires are made in Europe. Euro-Metric tires do also have different load capacities.
  • Numbers 225: The first three digits on our tires are reading “225”. This means that the tire width of our tire from sidewall to sidewall is 225 millimeters wide. For example, a 195/55R15 tire is 195mm wide from sidewall to sidewall.
  • Numbers 55: The next two numbers we find on our tire tells us the Aspect Ratio. The aspect radio tells us which is the ratio of the tire’s width to its height. For example, a tire size of P225/55 R15 tire, the 55 means that the height is equal to 55% of the tire’s width.
  • Letter R: Letter R refers to how the tire was made. Almost all tires today are Radial tires, which also the R stands for. A radial tire means that the layers run radially across the tire.
  • Numbers 15: This number is the inner diameter in inch, or other words, what size of rims this tire fits on. In our example, this tire says it is a 15-inch tire, which means that we need 15″ rims.
  • Numbers 95: The next two numbers tell us the Load index of the tire. The Load Index describes the total max weight that the tire can handle when it is fully inflated. The higher the load index rating, the more weight it can handle. You need a tire load index chart to see the exact numbers.
  • Letter H: The last letter of the tire number combination tells us the tire’s Speed rating is designed for. For example, the letter H tells us that the tire is rated for a maximum of 130 mph or 210 km/h.

Written by:

Magnus is the owner and main author of MechanicBase. He has been working as a mechanic for over 10 years, and the majority of them specialized in advanced diagnostics and troubleshooting. He has also been a motorsport (drifting) driver for over 5 years.