Have you ever gone tire shopping and been baffled by looking at the size chart? It may be pretty tricky looking at those profound numbers and complicated symbols and having no clue what they signify. You wind up buying tires that do not fit your vehicles’ requirements in the worst-case scenario. Another issue is that using the wrong ones is wasteful and even unsafe.

Knowing how to identify the suitable size for your car may save you time and hassle. Oh yes, it can also save you money. And as a car owner, this means a lot. Few people aren’t familiar with those mixed numbers and letters displayed on the sidewall of a tire.

This post is all about knowing how to read tire sizing and its meanings. We’ll walk you through measurements & a chart guide. Keep on reading!

Importance of Finding the Proper One

Yes, tires must materially match into your car. Still, here are a few additional reasons why having the proper size is so important.

As per common perception, the only fundamental car component that touches the road is the tires. They are a part of a wheel setup built to support a vehicle’s entire weight. Aside from that, they are designed to absorb shocks and vibrations. They convey traction controls and speed. Braking forces are sent from the tire to the road surface. They keep and alter the direction of motion. They may come with resilient rubbers and are loaded with compressed air to accomplish such functions. The incorrect tire may hamper your car’s performance and endanger you on the road.

When it comes to tire changes, you should stick with the same size upon replacement. Settled on the type for your vehicle and stick to it. Having different sized tires may distort your gauges and impair your vehicle’s safety systems and stability control.

Switching bigger tires with the wrong sidewall diameter can compromise your vehicle’s steering system and tires. It can give false speedometer readings. The same may be said when switching smaller tires.

If at all possible, adhere to the same brand and size. Combining various complimentary items to form a matched set may lessen your vehicle’s overall performance.

Dimensions Explained

There are two types of measurements. Metric and flotation.

Metric units are used for most tires purchased by the general public and are relatively difficult to understand. P265/50R20 is one example.

There are six (6) sections in metric sizing.

#1. First letter

The tire type is the first letter in the code that indicates what class it is.

• “P” is a designation for passenger vehicle tires. It includes cars and minivans. It also covers SUVs and small pickup trucks. Lastly, it’s also for sedans.
• “LT” class stands for a light truck. It’s for vehicles carrying medium loads, including trailers. It’s also for other vehicles used for rough driving conditions and pickups and vans hauling heavy loads.
• “ST” means special trailer tires designed for vehicles carrying heavy loads. It includes utility trailers and boat trailers.
• “T” is for temporary rated or spare tires for speeds not exceeding 50 mph and for emergencies or driving just enough to get to a garage shop.

It is most likely a passenger tire if it does not specify the initial letter. Make careful you double-check the load rating.

#2. Width

The 3-digit number after the first letter is the width section. It (265) defines the width from sidewall to sidewall in millimeters when seen from the front.

#3. Aspect Ratio

The aspect ratio is often known as the tire profile size. It reflects the sidewall’s size in proportion to the section width. In this example, “50” indicates that the sidewall is 1⁄2 of the width. Or 5.2″. The higher or taller the sidewall, the higher or taller the ratio.

The following code is to determine the type of construction. In this example, R indicates that it is a radial structure.

• Radial ® tires now account for 98 percent of all the tires manufactured. Most vehicle owners prefer them because of their improved grip and gas mileage. They also have great durability. The plies of radial types are placed perpendicular to the direction of movement. It also indicates a mix of polyester cloth and steel covered with rubber.
• D-reading is present on some tires. It is an abbreviation for a diagonal ply or bias-ply, often known as the traditional X or cross-ply. This indicates that the plies are crisscrossed.
• Another letter is B. It denotes belt constructions, which are commonly seen on bikes or trailers. They’re similar to the ones that have a “D,” except they feature a belt that passes beneath the thread region.
• F is another type that indicates “run flat.” Simply said, it runs flat after being ruptured for a short period.

#4. Wheel Diameter

The wheel diameter is a two-digit value representing the wheel’s diameter in inches. It uses the same coding for the metric and US standard systems.

#5. Load Index or Service Description Rating

Load index or service description rating is used to identify your load factor and speed rating. Based on a conventional tire chart, it denotes how much weight a tire can hold.

#6. Speed Rating

The speed rating refers to the speed rating. It shows the maximum speed at which it is safe to drive over an extended time. A better speed rating can withstand more heat. As the speed rating increases, so does the construction quality and tire durability. A high rating also indicates a higher price.

Flotation sizing is simpler than metric sizing. A 40×25.50 R22LT flotation example is 40 inches tall, 5.5 inches wide. It fits your 22-inch tire.

Where to Find the Number to Look For?

An extensive tire size chart with metric and inch sizes easily compared all models. Each metric measurement includes both the metric size and the inch equivalent. To convert the metric unit to an inch, multiply the first number by the second number and divide by 100. It gives you the sidewall height in millimeters. Then divide that by 25.4 to convert it to an inch. The overall diameter is calculated by multiplying the wheel diameter by two sidewall measures. Then, divide the first value by 25.4 to get the width in inches.

Tire Chart by Wheel Size and Diameter

Here is a chart that lists every tire by wheel size and diameter to make your search as easy as possible.

chart for 13” wheels

Check below to see the various options for 13″ wheels. The upper number signifies the diameter.

21″   185/60R13 = 21.7×7.3R13 215/50R13 = 21.5X8.5R13 225/45R13 = 21×8.9R13 225/50R13 = 21.9×8.9R13 255/40R13 = 21x10R13	22″   155/80R13 = 22.8×6.1R13 175/70R13 = 22.6×6.9R13 205/60R13 = 22.7×8.1R13 22X8R13	23″   165/80R13 = 23.4X6.5R13 185/70R13 = 23.2×7.3R13
24″ Diameter   175/80R13 = 24×6.9R13 185/80R13 = 24.7×7.3R13 24.5X8R13 24.5X9R13

 

Chart for 14” wheels

19″   105/70R14 = 19.8X4.1R14	20″   115/70R14 = 20.3X4.5R14 125/70R14 = 20.9X4.9R14	21″   165/55R14 = 21.1X6.5R14
22″   135/80R14 = 22.5X5.3R14 165/65R14 = 22.4×6.5R14 185/55R14 = 22×7.3R14 185/60R14 = 22.7×7.3R14 195/55R14 = 22.4×7.7R14 205/50R14 = 22.1×8.1R14 205/55R14 = 22.9×8.1R14 225/50R14 = 22.9×8.9R14	23″   175/65R14 = 23×6.9R14 175/70R14 = 23.6×6.9R14 185/65R14 = 23.5×7.3R14 195/60R14 = 23.2×7.7R14 205/60R14 = 23.7×8.1R14	24″   185/70R14 = 24.2×7.3R14 185/75R14 = 24.9X7.3R14 195/65R14 = 24×7.7R14 195/70R14 = 24.7×7.7R14 215/60R14 = 24.2×8.5R14 225/60R14 = 24.6×8.9R14
25″   185R14 = 25.7×7.3R14 195/75R14 = 25.5×7.7R14 205/70R14 = 25.3×8.1R14 215/70R14 = 25.9×8.5R14 235/60R14 = 25.1×9.3R14 245/60R14 = 25.6×9.6R14	26″   195R14 = 26.2×7.8R14 205/75R14 = 26.1×8.1R14 215/75R14 = 26.7×8.5R14 225/70R14 = 26.4×8.9R14 26X8.5R14	27″   205R14 = 27×8.2R14 27X8.5R14 27X9.5R14
28″   28X10R14	30″   30X10R14

 

Chart for 15” wheels

20″   105/70R15 = 20.8X4.1R15	21″   115/70R15 = 21.3X4.5R15 125/70R15 = 21.9X4.9R15 165/50R15 = 21.5X6.5R15 195/45R15 = 21.9×7.7R15	22″   125/80R15 = 22.9X4.9R15 145/65R15 = 22.4×5.7R15 155/60R15 = 22.3×6.1R15 165/60R15 = 22.8×6.5R15 175/55R15 = 22.6×6.9R15 195/50R15 = 22.7×7.7R15 22X8R15 22.5X4.5R15 245/40R15 = 22.7X9.6R15 275/35R15 = 22.6×10.8R15
23″   135/80R15 = 23.5X5.3R15 165/65R15 = 23.4X6.5R15 175/60R15 = 23.3×6.9R15 185/55R15 = 23×7.3R15 185/60R15 = 23.7×7.3R15 195/55R15 = 23.4×7.7R15 205/50R15 = 23.1×8.1R15 205/55R15 = 23.9×8.1R15 225/45R15 = 23×8.9R15 225/50R15 = 23.9×8.9R15 295/35R15 = 23.1X11.6R15	24″   135/90R15 = 24.6X5.3R15 155/80R15 = 24.8X6.1R15 175/65R15 = 24×6.9R15 185/65R15 = 24.5×7.3R15 195/60R15 = 24.2×7.7R15 205/60R15 = 24.7×8.1R15 225/55R15 = 24.7×8.9R15 235/50R15 = 24.3×9.3R15 24X4.5R15 24X5R15 24.5X8R15 245/50R15 = 24.6×9.6R15 345/35R15 = 24.5×13.6R15	25″   165/80R15 = 25.4X6.5R15 185/70R15 = 25.2×7.3R15 195/65R15 = 25×7.7R15 195/70R15 = 25.7×7.7R15 205/65R15 = 25.5×8.1R15 215/60R15 = 25.2×8.5R15 225/60R15 = 25.6×8.9R15 265/50R15 = 25.4X10.4R15 275/50R15 = 25.8×10.8R15
26″   205/70R15 = 26.3×8.1R15 215/65R15 = 26×8.5R15 215/70R15 = 26.9×8.5R15 235/60R15 = 26.1×9.3R15 245/60R15 = 26.6×9.6R15 26X10R15 26X10.5R15 26X11.5R15 26X6R15 26X7.5R15 26X8R15 26X8.5R15 295/50R15 = 26.6×11.6R15	27″   205/75R15 = 27.1×8.1R15 215/75R15 = 27.7×8.5R15 225/70R15 = 27.4×8.9R15 255/60R15 = 27x10R15 27X10.5R15 27X9.5R15 27.5X4.5R15 295/55R15 = 27.8X11.6R15 325/50R15 = 27.8×12.8R15 E78-15 = 27×6.5R15	28″   225/75R15 = 28.3×8.9R15 235/70R15 = 28×9.3R15 235/75R15 = 28.9×9.3R15 245/70R15 = 28.5X9.6R15 255/65R15 = 28.1x10R15 275/60R15 = 28×10.8R15 28X10.5R15 28X11.5R15 28X12.5R15 28X13.5R15 28X4.5R15 28X7.5R15 28X9R15
29″   215/85R15 = 29.4X8.5R15 255/70R15 = 29.1x10R15 265/70R15 = 29.6×10.4R15 29X10.5R15 29X11.5R15 29X12.5R15 29X15.5R15 29X18R15 29X18.5R15 29X4.5R15 29X8.5R15 29.5X11.5R15 29.5X13.5R15 29.5X9R15 315/60R15 = 29.9×12.4R15 7R15 = 29.5×7.7R15	30″   255/75R15 = 30.1x10R15 265/75R15 = 30.6×10.4R15 295/65R15 = 30.1×11.6R15 30X10R15 30X10.5R15 30X11.5R15 30X12.5R15 30X13.5R15 30X7R15 30X9R15 30X9.5R15	31″   31X10.5R15 31X11R15 31X11.5R15 31X12.5R15 31X13R15 31X13.5R15 31X14.5R15 31X16.5R15 31X18R15 31X18.5R15 31X9.5R15
32″   32X10.5R15 32X11.5R15 32X14R15 32X16R15 32X17.5R15 32X18.5R15 32X9.5R15	33″   33X10.5R15 33X11.5R15 33X12.5R15 33X13R15 33X13.5R15 33X14R15 33X14.5R15 33X15.5R15 33X16.5R15 33X19.5R15 33X21.5R15 33X9R15 33X9.5R15	34″   34X10.5R15 34X12.5R15 34X9.5R15
35″   35X10.5R15 35X12.5R15 35X13.5R15 35X14.5R15 35X15R15 35X15.5R15 35X16R15	36″   36X12.5R15 36X13.5R15 36X14.5R15	37″   37X12.5R15 37X13R15 37X13.5R15 37X14R15 37X14.5R15
38″   38X12.5R15 38X13R15 38X14.5R15 38X15.5R15 38.5X11R15 38.5X13.5R15 38.5X14.5R15 38.5X15R15 38.5X16R15	39″   39X13.5R15 39.5X13.5R15 39.5X15R15 39.5X18R15	40″   40X16R15
42″   42X14R15 42X15R15 42.5X13.5R15	44″   44X18.5R15 44X19.5R15 44X21R15	47″   47X17R15

 

Chart for 16.5” wheels

29″ Diameter   8.75R16.5 = 29.5×8.8R16.5	30″ Diameter   9.5R16.5 = 30.6×9.5R16.5	32″ Diameter   32X12R16.5
33″ Diameter   33X11.5R16.5 33X12.5R16.5 33X14R16.5 33X14.5R16.5 33X15.5R16.5	35″ Diameter   35X12.5R16.5 35X14.5R16.5 35X15R16.5 35X15.5R16.5 35X16R16.5 35X9.5R16.5	36″ Diameter   36X12.5R16.5 36X13.5R16.5 36X14.5R16.5 36X16R16.5
37″ Diameter   37X12.5R16.5 37X13R16.5 37X14R16.5	38″ Diameter   38X11R16.5 38X12.5R16.5 38X15.5R16.5 38.5X11R16.5 38.5X13.5R16.5 38.5X14.5R16.5 38.5X15R16.5 38.5X16R16.5	42″ Diameter   42X14R16.5 42X15R16.5 42.5X13.5R16.5
44″ Diameter   44X18.5R16.5 44X18.5R16.5 44X19.5R16.5 44X21R16.5

Chart for 25” diameter

14″ Wheel   185R14 = 25.7×7.3R14 195/75R14 = 25.5×7.7R14 205/70R14 = 25.3×8.1R14 215/70R14 = 25.9×8.5R14 235/60R14 = 25.1×9.3R14 245/60R14 = 25.6×9.6R14	15″ Wheel   165/80R15 = 25.4X6.5R15 185/70R15 = 25.2×7.3R15 195/65R15 = 25×7.7R15 195/70R15 = 25.7×7.7R15 205/65R15 = 25.5×8.1R15 215/60R15 = 25.2×8.5R15 225/60R15 = 25.6×8.9R15 265/50R15 = 25.4X10.4R15 275/50R15 = 25.8×10.8R15	16″ Wheel 135/90R16 = 25.6X5.3R16 145/80R16 = 25.1X5.7R16 195/60R16 = 25.2×7.7R16 205/60R16 = 25.7×8.1R16 215/55R16 = 25.3×8.5R16 225/55R16 = 25.7×8.9R16 245/50R16 = 25.6×9.6R16 265/45R16 = 25.4X10.4R16 275/45R16 = 25.7×10.8R16 315/40R16 = 25.9X12.4R16
17″ Wheel   115/95R17 = 25.6X4.5R17 135/80R17 = 25.5X5.3R17 145/70R17 = 25X5.7R17 155/70R17 = 25.5X6.1R17 205/50R17 = 25.1×8.1R17 205/55R17 = 25.9×8.1R17 215/50R17 = 25.5X8.5R17 225/45R17 = 25×8.9R17 225/50R17 = 25.9×8.9R17 235/45R17 = 25.3×9.3R17 245/45R17 = 25.7×9.6R17 255/40R17 = 25x10R17 265/40R17 = 25.3×10.4R17 275/40R17 = 25.7×10.8R17 295/35R17 = 25.1×11.6R17 315/35R17 = 25.7×12.4R17	18″ Wheel   135/70R18 = 25.4X5.3R18 155/60R18 = 25.3X6.1R18 215/45R18 = 25.6×8.5R18 225/40R18 = 25.1×8.9R18 235/40R18 = 25.4×9.3R18 245/40R18 = 25.7×9.6R18 255/35R18 = 25x10R18 265/35R18 = 25.3×10.4R18 275/35R18 = 25.6×10.8R18 285/35R18 = 25.9×11.2R18 295/30R18 = 25×11.6R18 305/30R18 = 25.2x12R18 315/30R18 = 25.4×12.4R18 335/30R18 = 25.9×13.2R18	19″ Wheel 115/70R19 = 25.3X4.5R19 125/70R19 = 25.9X4.9R19 225/35R19 = 25.2×8.9R19 235/35R19 = 25.5×9.3R19 245/35R19 = 25.8×9.6R19 255/30R19 = 25x10R19 265/30R19 = 25.3×10.4R19 275/30R19 = 25.5×10.8R19 285/30R19 = 25.7×11.2R19 315/25R19 = 25.2×12.4R19
20″ Wheel   215/30R20 = 25.1X8.5R20 225/30R20 = 25.3×8.9R20 235/30R20 = 25.6×9.3R20 245/30R20 = 25.8×9.6R20 275/25R20 = 25.4X10.8R20 285/25R20 = 25.6×11.2R20 295/25R20 = 25.8×11.6R20

Types

Touring

Touring ones provide a smoother ride with adequate wet and dry grip. They have increased winter traction, but are not suitable for a summer drive. They provide a comfortable drive and extended tread life.

Performance

These emphasize quick handling and improved wet and dry grip. There’s adequate winter traction and a sporty quality. It has more pointed tread life.

All-terrain

Engineered for daring, they have exceptional off-road traction. They’re louder and firmer on surface streets. Winter traction is adequate, and the wear life is decent.

Winter

Winter ones are specialists in snow and sleet. They have a good ice grip and are designed to drive in low temperatures.

Track

These are for the racetrack or autocross. The tires have incredible track performance while providing agile handling. Unfortunately, they have a short life. Some are appropriate for usage on the street, but not all.

Special service

Trailer service tires that are designed for balance, endurance, and loading.

FAQ