How to Read Tire Size: Meaning, Measurements & Chart Guide

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.

car tires

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

tire from the left

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.

tire seen from above

#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.

tire seen from the center

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

tire seen from the right

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.

tires at a car shop

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

What does 265 70r17 mean?

It means the tire has a 265 mm tread width. The 70 refers to the ratio between the height of the sidewall to tread width. The inner rim mounting diameter is 17 inches, and it’s a radial tire.

What does 33X12 50R20 mean?

It means it has an inner rim mounting diameter of 20 inches and a width of 12 inches. The sidewall is 50% of the tread width.

Can I use 225 tires instead of 235?


It depends on the car, but it’s sometimes possible.

Can I use 205 tires instead of 215?


Yes, it should work fine in most cases.

tires

Time needed: 3 minutes.

How to find the tire size on a car

  1. Open the door of your car.

  2. Check the information sticker on the side of the door.

  3. Look up the information in the manual, which you will usually find in the glove compartment.

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