How to Read Tire Size Visual guide to understanding every number on your tire sidewall
P225/65R17 102H
P — Type
P = Passenger vehicle tire
LT = Light Truck
ST = Special Trailer
No letter = Euro-metric
LT = Light Truck
ST = Special Trailer
No letter = Euro-metric
225 — Width
Section width in millimeters — the distance from one sidewall to the other when mounted. 225mm = 8.9 inches.
65 — Aspect Ratio
Sidewall height as a percentage of width. 65% of 225mm = 146.3mm sidewall. Lower = sportier. Higher = more comfortable.
R17 — Construction & Rim
R = Radial construction (99% of tires).
17 = Fits a 17-inch diameter wheel.
17 = Fits a 17-inch diameter wheel.
102 — Load Index
Maximum weight capacity per tire. 102 = 1,874 lbs (850 kg). Must meet or exceed vehicle specs. Full chart →
H — Speed Rating
Maximum safe sustained speed. H = 130 mph (210 kph). Must meet or exceed vehicle specs. Full chart →
Overall Diameter Calculation
(Width × Aspect ÷ 100 × 2) + (Rim × 25.4)
(225 × 65 ÷ 100 × 2) + (17 × 25.4) = 724.3 mm (28.5")
(225 × 65 ÷ 100 × 2) + (17 × 25.4) = 724.3 mm (28.5")
Tire Size Decoder
Select any tire size to see its full breakdown
/
R
225/65R17
Sidewall Height
146.3 mm
225 x 65% = 146.3
Overall Diameter
724.3 mm
28.5"
Circumference
2276 mm
89.6"
Revs/Mile
707
Width (inches)
8.9"
Inch Equivalent
28.5x8.9R17
Where to Find Your Tire Size
Your tire size is printed on three places:
- Tire sidewall — Look for the prominent number like P225/65R17 102H molded into the rubber.
- Driver's door jamb sticker — Open the driver's door and look for the sticker on the door frame or the door edge. This shows the manufacturer's recommended tire size AND inflation pressure.
- Owner's manual — The specifications section lists all approved tire sizes for your vehicle.
You can also look up your tire size by vehicle — enter your make, model, and year.
Understanding Aspect Ratio
The aspect ratio dramatically affects how a tire looks, rides, and handles:
Low Profile (25-45)
🏎
Sporty handling, firm ride, more road noise. Common on performance cars.
Standard (50-65)
🚗
Balanced ride and handling. Most popular range for sedans and SUVs.
High Profile (70-85)
🚚
Soft, comfortable ride. Better off-road. Common on trucks and older vehicles.
DOT Date Code — How Old Are Your Tires?
Every tire has a DOT (Department of Transportation) code stamped on the sidewall. The last four digits tell you when the tire was manufactured:
DOT XXXX XXXX 2319
23 = Week 23 (early June)
19 = Year 2019
This tire was manufactured in the 23rd week of 2019. Most tire manufacturers and safety organizations recommend replacing tires that are 6-10 years old, regardless of tread depth, because rubber compounds degrade over time.
Frequently Asked Questions
The R stands for Radial construction, which is the most common type of tire construction today. In a radial tire, the cord plies run perpendicular to the direction of travel. Nearly all modern passenger tires are radial. You may rarely see D (diagonal/bias ply) on trailer tires or B (belted bias) on some older tire designs.
The number after R is the rim diameter in inches. For example, in 225/65R17, the 17 means this tire fits a 17-inch wheel. Common rim diameters range from 14" to 22" for passenger vehicles, with 17" being the most popular size in the current market.
The aspect ratio is the second number in the tire size (e.g., 65 in 225/65R17). It represents the height of the sidewall as a percentage of the tire's width. So a 225/65R17 tire has a sidewall height of 225 × 0.65 = 146.25mm. Lower aspect ratios (30-45) mean a shorter sidewall for sportier handling. Higher ratios (60-80) mean a taller sidewall for a more comfortable ride.
You can find your tire size in several places: 1) On the tire sidewall itself — look for a number like 225/65R17. 2) On the driver's door jamb sticker (inside the door frame). 3) In your vehicle owner's manual. 4) On this website — search by your vehicle make, model, and year. The door jamb sticker shows the manufacturer's recommended size and inflation pressure.
After the size (e.g., 225/65R17), you'll typically see two more numbers and a letter, like 102H. The number (102) is the load index — the maximum weight each tire can support (102 = 1,874 lbs). The letter (H) is the speed rating — the maximum safe speed (H = 130 mph / 210 kph). These ratings must meet or exceed your vehicle manufacturer's specifications.