Euro-Metric and P-Metric Tire Sizes Explained

Tire sizes can be a little puzzling if you don’t know what you’re looking at. What makes it even more complicated is that there’s more than one tire size standard used in the world. Two of the most common ones are P-metric and Euro-metric. But what do these tire sizes mean and are they interchangeable?

What Do “P-Metric” and “Euro-Metric” Mean?

Let’s start with what the “P” and “Euro” mean in these tire sizes. The “P” stands for passenger, because this type of tire was originally designed for passenger-type vehicles. This sizing was standardized by The Tire & Rim Association, Inc. in the 70s. The association is based in the US.

Euro-metric sizing is also made with passenger-type vehicles in mind. It was standardized by the European Tyre and Rim Technical Organization in the 60s. The Euro-metric commercial tires, also known as the C-type tires, were also standardized by this organization.

Differences and Similarities Between P-Metric and Euro-Metric Tire Sizes

P-metric and Euro-metric tires aren’t too different, but there are still a few traits in each that you should be aware of when purchasing a set. Here are the different tire size traits explained:

Size Names

P-metric tires will have a “P” in front of the tire size as seen on the tire’s sidewall. The lack of a “P” means the tire was manufactured and measured using Euro-metric parameters. Euro-metric commercial tires have a “C” before their names. The numbers following the letter (or lack thereof) typically indicate the size of the tire. As long as this string of numbers and letters are the same, it means the tires have the same dimensions and will appear to fit the same vehicles interchangeably.

That being said, the two- or three-digit number after the size is called the load index and is explained in the next section.

Load Capacity Calculations

Load capacity calculations are run to determine a tire’s load index. The load index is a numeric code indicating the maximum weight a tire can sustain while inflated to its maximum permitted air pressure. The calculations are made with severe conditions in mind. The higher a tire’s load index is, the greater its load-carrying capacity.

Now, the load capacity index numbers aren’t easy to understand at a glance, so you can check an online load index calculator for help. P-metric and Euro-metric tires can have different load and inflation formulas, so make sure you’re using the correct calculator or table when you check.

In general though, you’ll more often notice a difference between the two passenger tire types and the Euro-metric commercial type of tires. Because Euro-metric commercial tires are made and designed for heavy duty light trucks and vans, these are made with higher load capacity maximums.

Inflation Pressure Tables

The inflation pressure tables of P-metric and Euro-metric tires also tend to differ slightly. Tire inflation pressure tables are based on the amount of air that the tire manufacturers recommend for their products. You can check the manufacturer’s pressure tables to see how different the inflation pressures are between P-metric and Euro-metric tires.

Are P-Metric and Euro-Metric Tires Interchangeable?

Euro-metric and Euro-metric commercial tires generally have greater load capacity than P-metric tires. This means you can easily use them in vehicles that originally came with P-metric tires, but the reverse is not as simple.

Certain industry specialists recommend that, because of the difference in load capacities, you shouldn’t use the P-metric tire size counterpart if your vehicle came with Euro-metric tires. That being said, you can always ask a professional tire dealer or mechanic with access to a tire fitment guide if a P-metric tire can work with your vehicle regardless.

Euro-metric and P-metric tires of the same numeric size share performance categories and speed ratings. Thus, they’re functionally identical and somewhat interchangeable if you use them in sets of four or axle pairs.

In general, it’s a good rule of thumb to use whatever tire type came with your vehicle, whether it’s a P-metric tire size or a Euro-metric one. When in doubt, consult a professional.