How to Read Your Tire Size: What the Numbers and Letters Mean

The Short Answer

Your tire size is printed on the sidewall and on a placard inside the driver's door. In a code like 225/65R17 102H, 225 is the tire's width in millimetres, 65 is the sidewall height as a percentage of that width, R means radial construction, 17 is the rim diameter in inches, 102 is the load index (how much weight each tire can carry), and H is the speed rating. The safest way to buy tires is to match the size, load index and speed rating on your door placard.

Where to Find Your Correct Tire Size

• The tire placard on the driver's door frame (or sometimes the fuel door or glovebox). This is the size the manufacturer specifies for your vehicle.
• Your owner's manual.
• The sidewall of your current tires — but only if they're the original size. A previous owner may have fitted something different.

If the placard and your current tires don't match, go by the placard, or ask us to check.

Reading the Code, Part by Part

Using 225/65R17 102H as the example:

• 225 — section width: the tire is 225 mm wide from sidewall to sidewall.
• 65 — aspect ratio: the sidewall height is 65% of the width. A lower number means a shorter, sportier sidewall.
• R — construction: radial, which is what nearly every passenger tire is today.
• 17 — rim diameter: fits a 17-inch wheel. This must match your rim exactly.
• 102 — load index: a code for the maximum weight each tire can carry at its rated pressure.
• H — speed rating: the maximum sustained speed the tire is rated for.

Some sizes start with letters: P (passenger) or LT (light truck). LT tires are built for heavier loads and towing, and they're common on pickup trucks.

Load Index and Speed Rating: What 91V, 94W and XL Mean

The two characters after the size work together. The number is the load index and the letter is the speed rating. A few common ones:

• Load index 91 = 615 kg per tire; 94 = 670 kg; 102 = 850 kg.
• Speed rating T = 190 km/h; H = 210 km/h; V = 240 km/h; W = 270 km/h; Y = 300 km/h.

So the difference between 91V and 94W is that the 94W tire can carry more weight per tire (670 kg vs 615 kg) and is rated for a higher top speed (270 km/h vs 240 km/h). XL means extra load: a reinforced tire that can carry a higher load at a higher inflation pressure than a standard tire of the same size.

The rule: replacement tires should have a load index and speed rating at least as high as your vehicle's placard calls for. Going lower on load index is never a good idea, especially on SUVs and trucks. Many winter tires carry a lower speed rating than the original summer or all-season tires, and that's generally accepted for winter tires — ask us if you're unsure for your vehicle.

Other Markings Worth Knowing

• The three-peak mountain snowflake symbol: the tire meets a severe-snow traction standard. Look for it on winter and all-weather tires.
• M+S: mud and snow. Common on all-season tires, but not the same as the snowflake symbol.
• DOT date code: the last four digits show the week and year the tire was made — 4524 means the 45th week of 2024.

Get the Right Size, Every Time

Send us a photo of your door placard or tire sidewall, and we'll confirm the size and show you options at different price points. Shop tires or contact us. For SUVs and pickup trucks, our SUV & truck tire fitment guide goes deeper on load ratings, and How Much Do New Tires Cost in Ontario? explains how size affects price.