Reference Chart

Tire Size Chart & Decoder

Q: How do I read a tire size?

A tire size like P225/65R17 92H decodes as: P = passenger car, 225 = section width in mm, 65 = aspect ratio (sidewall is 65% of width), R = radial construction, 17 = rim diameter in inches, 92 = load index (rating for max weight), H = speed rating (max speed). Read each component to know what fits your vehicle.

Q: What does 225/65R17 mean?

225 = tire width in millimeters (225 mm = 8.86 inches). 65 = aspect ratio, meaning the sidewall height is 65% of the width (146 mm = 5.75 inches). R = radial construction. 17 = wheel diameter in inches. Overall tire diameter is 17 inches + 2 sidewalls = approximately 28.5 inches.

Q: Can I put a different size tire on my car?

Yes, within a limited range called the 'plus sizing' or 'minus sizing' window. The overall tire diameter must stay within about 3% of the OEM size to avoid speedometer errors, suspension clearance issues, and ABS/traction control faults. The width can typically vary by 10 to 20 mm without issue. Always confirm fitment with a tire fitment chart for your specific vehicle.

Q: What is tire load index?

A two- or three-digit number indicating the maximum weight the tire can carry. Index 91 = 1356 lb. Index 95 = 1521 lb. Index 100 = 1764 lb. Index 110 = 2337 lb. Always match or exceed the OEM load index. The total of all four tires must support the vehicle's gross weight rating.

Q: What does H, V, or W mean on a tire?

These are speed ratings. H = max 130 mph (210 km/h). V = max 149 mph (240 km/h). W = max 168 mph (270 km/h). Y = max 186 mph (300 km/h). The speed rating indicates the maximum sustained speed the tire is designed for, not a recommended cruising speed. Match or exceed the OEM rating.

Q: What is the difference between a P-metric and LT tire?

P = passenger car (lighter construction, optimized for ride comfort and fuel economy). LT = light truck (heavier-duty construction with reinforced sidewalls for higher loads and towing). LT tires use different load and pressure standards. Don't mix P and LT tires on the same vehicle.

Q: How do I read an off-road tire size like 33x12.50R17?

This is flotation/imperial sizing used for light trucks and off-road tires. 33 = overall tire diameter in inches. 12.50 = section width in inches. R = radial. 17 = wheel diameter in inches. So a 33x12.50R17 is 33 inches tall, 12.5 inches wide, on a 17-inch wheel. Easier to visualize than metric sizes.

Q: How long do tires last?

Most modern tires last 40,000 to 60,000 miles. Premium tires can exceed 70,000. Performance tires often last only 20,000 to 30,000. Regardless of mileage, replace tires at 6 to 10 years from manufacture date due to rubber degradation. Check the DOT code on the sidewall (last 4 digits = week/year of manufacture).

Q: What does the DOT code on a tire mean?

The Department of Transportation code identifies the tire factory, size, type, and manufacture date. The last 4 digits are the date: first 2 = week of year, last 2 = year. For example, 1224 = the 12th week of 2024. Tires older than 10 years should be replaced regardless of tread depth due to rubber degradation.

Q: What is the safest tread depth?

New tires have ~10/32 inch (8 mm) of tread. The legal minimum in most US states is 2/32 inch. The penny test: insert a penny with Lincoln's head down; if you can see all of his head, tread is below 2/32 inch and the tire is unsafe. Modern recommendation: replace at 4/32 inch (3 mm) for safer wet-weather performance, especially before winter.

Tire sidewalls are covered in numbers and letters that mean specific things. This page decodes every part of a tire size code (P225/65R17 92H, for example) and gives you reference charts for load index, speed rating, and the most common tire sizes by vehicle type. Includes metric-to-inch conversions for off-road and light-truck sizes.

How to Read a Tire Size

Example size: P225/65R17 92H. Each part has meaning.

Code	Meaning	Detail
P	Tire type	P = Passenger car. LT = Light Truck. ST = Special Trailer. No letter = European metric (works on passenger cars). T = Temporary spare.
225	Section width	Width of the tire from sidewall to sidewall in millimeters. 225 mm = 8.86 inches.
65	Aspect ratio	Height of sidewall as a percentage of width. 65 means sidewall = 65% of 225 mm = 146 mm (5.75 inches).
R	Construction	R = Radial (modern standard). D = Diagonal/Bias (older, rare). B = Belted bias.
17	Rim diameter	The wheel diameter in inches that this tire fits. Common: 15, 16, 17, 18, 19, 20.
92	Load index	Maximum weight per tire. 92 = 1,389 lb. See load index table below.
H	Speed rating	Maximum sustained speed. H = 130 mph. See speed rating table below.

Overall Tire Diameter Calculation

To find the overall tire diameter from a size code:

Diameter (mm) = Rim diameter (mm) + 2 × Sidewall height (mm)

Where sidewall height = section width × aspect ratio ÷ 100.

Example for 225/65R17: 17 inches = 432 mm. Sidewall = 225 × 65 / 100 = 146 mm. Total = 432 + 2 × 146 = 724 mm = 28.5 inches.

Other Sidewall Markings

M+S: Mud and Snow. All-season tire.
3-peak mountain snowflake: Severe snow service rating. True winter tire.
DOT XXXX YYYY ZZZZ NNNN: Department of Transportation code. Last 4 digits = week and year of manufacture (e.g., 1224 = 12th week of 2024).
UTQG: Treadwear, Traction, Temperature grades. Treadwear is a relative comparison (300 is twice as wear-resistant as 150). Traction A-C. Temperature A-C.
Max load and pressure: Maximum tire load capacity and the pressure at which it's measured.
RFT, ZP, SSR, MOExtended: Run-flat designations from different manufacturers.

Tire Load Index Chart

Maximum weight each tire can carry, indicated by a two- or three-digit code on the sidewall. All four tires together must support the gross vehicle weight.

Index	Lbs / Tire	Kg / Tire	Index	Lbs / Tire	Kg / Tire
75	853	387	100	1,764	800
80	992	450	102	1,874	850
82	1,047	475	104	1,984	900
84	1,102	500	106	2,094	950
86	1,168	530	108	2,205	1,000
88	1,235	560	110	2,337	1,060
90	1,323	600	112	2,469	1,120
91	1,356	615	115	2,679	1,215
92	1,389	630	118	2,910	1,320
93	1,433	650	120	3,086	1,400
94	1,477	670	125	3,638	1,650
95	1,521	690	128	4,079	1,850
96	1,565	710	130	4,409	2,000
97	1,609	730	133	4,807	2,180
98	1,653	750	135	5,071	2,300
99	1,709	775	140	5,952	2,700

Always match or exceed the OEM load index. Going below can cause tire failure, void warranties, and fail safety inspections. Going above is fine but doesn't necessarily improve ride or handling.

Tire Speed Rating Chart

The maximum sustained speed the tire can handle. Not a recommendation: just the engineered limit. Always meet or exceed the OEM rating.

Code	Max Speed (mph)	Max Speed (km/h)	Typical Use
L	75 mph	120 km/h	Off-road and light truck tires
M	81 mph	130 km/h	Temporary spare tires
N	87 mph	140 km/h	Temporary spare tires
P	93 mph	150 km/h	Some light truck tires
Q	99 mph	160 km/h	Winter tires, light truck
R	106 mph	170 km/h	Heavy-duty light truck
S	112 mph	180 km/h	Family sedans, vans
T	118 mph	190 km/h	Family sedans, minivans
U	124 mph	200 km/h	Sedans, coupes
H	130 mph	210 km/h	Sport sedans, coupes (very common)
V	149 mph	240 km/h	Sport sedans, coupes
W	168 mph	270 km/h	Sports cars, performance sedans
Y	186 mph	300 km/h	Performance and exotic cars
(Y)	186+ mph	300+ km/h	Top-tier supercars (theoretical limit unbounded)

Common Tire Sizes by Vehicle Type

Typical OEM tire sizes for the most common vehicle categories. Your specific vehicle's size will be in the owner's manual and on the driver's door jamb sticker.

Vehicle Type	Common Sizes	Diameter
Compact car (Civic, Corolla)	195/65R15, 205/55R16, 215/45R17	~25″
Midsize sedan (Accord, Camry)	215/55R17, 225/50R17, 235/45R18	~26–27″
Full-size sedan (Charger, Impala)	225/60R18, 235/55R18, 245/45R20	~28″
Sport coupe (Mustang, Camaro)	235/55R17, 245/45R19, 255/40R20	~27–28″
Compact SUV (RAV4, CR-V)	225/65R17, 235/55R19, 235/60R18	~28″
Midsize SUV (Highlander, Pilot)	235/65R18, 245/60R18, 255/55R19	~30″
Full-size SUV (Tahoe, Suburban)	275/60R20, 275/55R20, 285/45R22	~33″
Half-ton truck (F-150, 1500)	275/65R18, 275/60R20, LT265/70R17	~32–33″
Heavy-duty truck (F-250, 2500)	LT275/70R18, LT265/70R18, LT275/65R20	~33–34″
Off-road / Lifted truck	33x12.50R17, 35x12.50R17, 37x12.50R17	33–37″
Minivan (Sienna, Pacifica)	235/60R18, 235/55R19	~28″
Compact EV (Model 3, Bolt)	235/45R18, 235/40R19, 245/35R20	~26–27″
Electric SUV (Model Y, Mach-E)	255/45R19, 255/35R21	~28″

Flotation / Off-Road Tire Sizes (Imperial)

Off-road and light-truck tires often use imperial sizing: overall diameter x width on rim diameter. Easier to visualize than metric for big tires.

Imperial Size	Metric Equivalent	Use
30x9.50R15	235/75R15	Light off-road, jeep stock
31x10.50R15	265/75R15	Stock/mild lift trucks and SUVs
32x11.50R15	285/75R15	Mild lift trucks
33x12.50R15	305/75R15	2–3″ lift
33x12.50R17	305/70R17	2–3″ lift, newer trucks
35x12.50R17	325/65R17	3–6″ lift
35x12.50R20	325/55R20	3–6″ lift, larger wheels
37x12.50R17	355/65R17	4–8″ lift, serious off-road
40x13.50R17	375/70R17	Extreme off-road builds

Tire Buying & Replacement Guide

When to Replace Tires

Three factors trigger replacement:

Tread depth. Legal minimum is 2/32 inch in most US states. Better safety threshold is 4/32 inch for wet conditions and 5/32 inch for snow. New tires start at 10/32 to 12/32.
Age. Rubber degrades from heat, UV, ozone, and time. Replace tires older than 6 to 10 years from the manufacture date (last 4 digits of DOT code), regardless of tread depth. NHTSA recommends 6 years for full-time replacement, 10 years absolute maximum.
Damage. Sidewall bubbles, cracks, punctures outside the tread area, or impact damage require replacement, not repair.

The Penny Test

Place a US penny upside-down (Lincoln's head pointing into the tread groove) at multiple points around the tire. If you can see all of Lincoln's head, tread depth is below 2/32 inch and the tire is below the legal minimum. For wet-weather safety, use a quarter: if you can see all of Washington's head, tread is below 4/32 inch.

Tire Pressure

Use the pressure listed on the driver's door jamb sticker (not the max pressure on the tire sidewall, which is the maximum the tire can hold, not the recommended pressure). Most passenger cars run 30 to 35 PSI. Check pressure monthly. Underinflated tires wear unevenly, reduce fuel economy, and risk blowout at highway speeds. Overinflated tires have a harsher ride and reduced contact patch.

Tire Rotation

Rotate every 5,000 to 8,000 miles to equalize wear across all four tires. Most front-wheel-drive cars wear the front tires faster. Rotation pattern depends on whether the tires are directional or not, and on the drivetrain. Cross-rotate (front to back swap and left/right swap) for non-directional tires. Front-to-back only for directional. Some all-wheel-drive vehicles require all four tires to be within 2/32 inch of each other to avoid drivetrain damage.

All-Season vs Winter vs Summer

All-season: A compromise tire that works in most US climates but is mediocre in snow and ice. Marked M+S (mud and snow).
Winter / Snow tires: Soft rubber compound that stays flexible in cold; aggressive tread for snow and ice. Marked with the 3-peak mountain snowflake symbol (3PMSF). Required in some regions during winter. Wear quickly in warm weather.
Summer / Performance: Stiff compound for grip on warm, dry pavement. Useless or dangerous below 45°F. Maximum dry-road grip and steering response.
All-weather (relatively new): Bridges the gap between all-season and winter. Carries the 3PMSF symbol while still being acceptable in warm weather.

Plus Sizing and Minus Sizing

Plus sizing: go up a wheel diameter, drop the aspect ratio. Plus-1 means +1 inch wheel, -10 to -15 aspect ratio. Plus-2 is +2 inches and a corresponding drop. The goal is to keep the overall tire diameter the same so the speedometer remains accurate and the suspension geometry doesn't change. Plus sizing changes appearance, sharpens handling, but reduces ride comfort and increases pothole/rim damage risk.

Minus sizing: opposite direction. Smaller wheel, taller sidewall. Improves ride comfort and reduces vulnerability to wheel damage. Common for winter setups.

Frequently Asked Questions

How do I read a tire size?

Decode each segment of a code like P225/65R17 92H. P = passenger. 225 = width in mm. 65 = aspect ratio. R = radial. 17 = wheel diameter in inches. 92 = load index. H = speed rating.

What does 225/65R17 mean?

225 mm wide, sidewall is 65% of width (146 mm), radial construction, 17-inch wheel. Overall diameter approximately 28.5 inches.

Can I put a different size tire on my car?

Yes, within plus/minus sizing limits. Overall diameter should stay within 3% of OEM. Width can vary 10 to 20 mm. Always verify fitment.

What is tire load index?

Number indicating max weight per tire. 91 = 1356 lb. 95 = 1521 lb. 100 = 1764 lb. Match or exceed OEM.

What does H, V, or W mean on a tire?

Speed ratings. H = 130 mph. V = 149 mph. W = 168 mph. Y = 186 mph. Match or exceed OEM rating.

What is the difference between a P-metric and LT tire?

P = passenger car. LT = light truck (reinforced sidewalls, higher loads). Different load and pressure standards. Don't mix.

How do I read an off-road tire size like 33x12.50R17?

Imperial sizing: 33 inches overall diameter, 12.5 inches wide, radial, 17-inch wheel.

How long do tires last?

40,000 to 60,000 miles typically. Replace at 6 to 10 years from manufacture date regardless of mileage. Check DOT code.

What does the DOT code on a tire mean?

Department of Transportation code identifying factory, size, type, and manufacture date. Last 4 digits = week and year (1224 = week 12 of 2024).

What is the safest tread depth?

Legal minimum is 2/32 inch. Replace at 4/32 for wet weather safety. The penny test: if you see all of Lincoln's head, tire is below 2/32.

Mini About Us

We built this because tire shops talk about sizes assuming you already know what the numbers mean, and that's not where most people start. One page that decodes the whole sidewall and tells you what each number means for daily driving. This site is a part of the ads4good Network.

Tire Size Chart &amp; Decoder