A tire sidewall is packed with codes, numbers, and symbols that tell you everything about a tire's size, construction, capabilities, and safety certifications. Decoding the alphanumeric string like P215/65R15 95H reveals the vehicle type, width in millimeters, aspect ratio, construction type, rim diameter, load capacity, and maximum speed rating — all critical for choosing the right replacement tire.
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Try a standard format like P215/65R15 95H or click one of the sample codes above.
Click any segment in the tire code above, or select a card on the left to see a detailed explanation.
Computed Dimensions
Other Sidewall Markings
The DOT code certifies US safety compliance. The last 4 digits are the manufacture date — WWYY format (week + year).
Treadwear: Relative wear index. 100 = baseline. 400 lasts ~4× longer. Higher is better.
Traction: Wet stopping distance. AA (best) → A → B → C. Choose A or AA for safety.
Temperature: Heat resistance at speed. A (best) → B → C. A-rated for highway driving.
M+S (Mud + Snow): Self-certified by manufacturer. Basic all-season capability.
3PMSF (Three-Peak Mountain Snowflake): Government-tested winter certification. Required for chains-required roads in many states.
Max PSI: Maximum cold inflation pressure. Not the recommended daily pressure — check your door jamb sticker for that.
Max Load: Maximum weight per tire at max inflation. Always use load index from your vehicle spec sheet, not the max on the tire.
Load Index Reference
| Index | lbs | kg | Index | lbs | kg |
|---|
Speed Rating Reference
| Symbol | Max Speed (mph) | Max Speed (km/h) | Typical Use |
|---|
Common Tire Sizes by Vehicle Type
| Vehicle Type | Example Size | Width (mm) | Aspect Ratio | Rim (in) |
|---|---|---|---|---|
| Compact car | P195/65R15 | 195 | 65 | 15 |
| Mid-size sedan | P215/60R16 | 215 | 60 | 16 |
| Full-size sedan | P225/55R17 | 225 | 55 | 17 |
| Crossover / SUV | P235/60R18 | 235 | 60 | 18 |
| Performance car | 245/40R18 | 245 | 40 | 18 |
| Light-duty truck | LT245/75R16 | 245 | 75 | 16 |
| Full-size truck | LT265/70R17 | 265 | 70 | 17 |
| Heavy-duty truck | LT285/70R17 | 285 | 70 | 17 |
How to Read a Tire Sidewall
Every tire sold in the United States carries a standardized set of markings molded directly into the sidewall. Once you know the code, you can verify fitment, compare load and speed ratings, check manufacturing date, and understand winter capability — all without a dealer visit.
Step 1: Find the Tire Size String
Look on the tire sidewall for a string that starts with a letter prefix and contains a slash — for example, P215/65R15 95H. This is the primary tire size designation. It tells you everything about the tire's physical dimensions and performance ratings.
Step 2: Decode the Vehicle Type Prefix
The letter(s) before the numbers indicate the intended vehicle type. P (Passenger) covers cars and light SUVs. LT (Light Truck) covers pickups, vans, and trucks designed for heavier payloads. ST (Special Trailer) is for trailer tires only — never install ST tires on a vehicle. Some tires have no prefix, indicating European metric sizing with slightly different load standards from P-metric.
Step 3: Read the Three-Part Size Code
The numbers in the format 215/65R15 break down as: the first number is the section width in millimeters (215 mm), the second number is the aspect ratio as a percentage (sidewall height = 65% of width = 139.75 mm), and the number after R is the rim diameter in inches (15 inches). The letter R stands for Radial construction — the most common type today. B indicates Bias-ply and D indicates Diagonal construction.
Step 4: Look Up the Load Index and Speed Rating
After the tire size you will find a two-or-three-digit number (load index) followed by a letter (speed rating). Load index 95 corresponds to 1,521 lbs per tire — multiply by 4 for total vehicle capacity. The speed rating letter H means the tire is certified for sustained speeds up to 130 mph. Always match or exceed your vehicle's original equipment specifications for both values.
Step 5: Check the DOT Code for Tire Age
Find the DOT code, which begins with the letters "DOT" followed by a string of characters. The last four digits are the manufacture date: the first two are the week (01–52) and the last two are the year. A code ending in 2423 means week 24 of 2023. Most manufacturers and safety organizations recommend replacing tires after 6–10 years regardless of tread depth, because rubber degrades over time.
Step 6: Understand UTQG and Winter Ratings
The UTQG (Uniform Tire Quality Grading) system shows three ratings: treadwear index (higher = longer lasting), traction grade (AA/A/B/C for wet stopping), and temperature grade (A/B/C for heat resistance). For winter capability, look for the 3PMSF (Three-Peak Mountain Snowflake) symbol — it certifies government-tested snow performance. The M+S label alone is a weaker, self-certified designation that does not guarantee true winter safety.
Frequently Asked Questions
Is this tire sidewall decoder free to use?
Yes, completely free. The tire sidewall decoder runs entirely in your browser with no signup, no account, and no data sent anywhere. Everything stays on your device.
What does the P mean at the start of a tire code?
The P stands for Passenger vehicle. It indicates the tire is designed for passenger cars. LT means Light Truck (for pickups, SUVs, and vans with heavier loads), and ST means Special Trailer. Some tires have no prefix, which indicates European metric sizing with slightly different load standards.
What is the aspect ratio on a tire?
The aspect ratio is the sidewall height expressed as a percentage of the tire's section width. For example, a 215/65R15 tire has a sidewall height of 139.75 mm (65% of 215 mm). Lower aspect ratios (e.g., 45) mean shorter, sportier sidewalls. Higher ratios (e.g., 75) mean taller sidewalls that absorb bumps better.
What does the load index number mean on a tire?
The load index is a numerical code representing the maximum weight each tire can carry at maximum inflation. For example, load index 95 means 1,521 lbs per tire. Multiply by 4 for total vehicle capacity. Never fit tires with a lower load index than the vehicle manufacturer specifies — this is a safety requirement.
What does the speed rating letter mean on a tire?
The speed rating is a letter code indicating the maximum sustained speed the tire is designed for. H-rated tires are rated for 130 mph, V-rated for 149 mph, and W-rated for 168 mph. Always match or exceed your vehicle's original equipment speed rating. Mixing speed ratings reduces the rating of the entire set to the lowest letter.
What is the DOT code on a tire?
The DOT (Department of Transportation) code certifies the tire meets US safety standards. The last four digits encode the manufacturing date: the first two digits are the week of manufacture and the last two are the year. For example, DOT code ending in 2423 means week 24 of 2023. Tires older than 6-10 years should be replaced regardless of tread depth.
What do UTQG ratings mean on a tire sidewall?
UTQG (Uniform Tire Quality Grading) is a US government rating system with three components. Treadwear is a comparative index (100 = baseline; 400 lasts roughly 4x longer). Traction grades (AA, A, B, C) measure wet stopping ability. Temperature grades (A, B, C) rate heat resistance at sustained high speeds. Look for at least Traction A and Temperature A for everyday driving.
What is the 3PMSF symbol on a tire?
The 3PMSF (Three-Peak Mountain Snowflake) symbol means the tire meets severe snow service requirements and is certified for winter driving conditions. It is more stringent than the M+S (mud and snow) designation, which is a self-certification by manufacturers. If you drive in heavy snow or ice, look for the 3PMSF symbol, not just M+S.