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. In the worst-case scenario, you may wind up purchasing ones that do not correctly fit your vehicles’ requirements. 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, hassle, and money. And as a car owner, this implies a lot. Yet, few people aren’t familiar with those mixed numbers and letters displayed on the sidewall.

Fortunately, this post is all about knowing how to read tire sizing, the meanings, measurements & chart guide. Keep on reading!

Importance of Finding the Proper One

Yes, tires must materially match into your car, but 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 set up built to support a vehicle’s entire weight. Aside from that, they are designed to absorb shocks and vibrations, convey traction controls, speed, and braking forces to the road surface, and keep and alter the direction of motion. They may come with resilient rubbers and are loaded with compressed air to accomplish such functions. Still, the incorrect tire one may hamper your car’s performance and possibly endanger you on the road.

When it comes to tire changes, once you’ve settled on the type for your vehicle, you should stick with the same size upon replacement. This is because having a different sized ones may distort your gauges, as well as impair your vehicle’s safety systems and stability control.

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

If at all can, adhere to the same brand and size because combining various complimentary items to form a matched set may deter your vehicle’s overall performance.

Dimensions Explained

There are two types of measurements; metric and flotation.

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

There are six (6) sections in metric sizing.

#1. First letter in

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

  • P designates for passenger vehicle tires, including cars, minivans, SUVs, small pickup trucks, and sedans.
  • LT class stands for light truck, for vehicles carrying medium loads, trailers, and other vehicles used for rough driving conditions, as well as pickups and vans hauling heavy loads.
  • ST means special trailer tires designed for vehicles carrying heavy loads, 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.

If it does not have the initial letter specified, it is most likely a passenger tire. Make careful you double-check the load rating.265

#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, often known as the tire profile size, 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 ones manufactured. Most vehicle owners prefer them because of their improved grip, gas mileage, and durability. The plies of radial these 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 in 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, which denotes belt constructions, which are commonly seen on bikes or trailers. They’re much the same as in D, except they feature a belt that passes beneath the thread region.
  • F is another type that simply indicates “run flat.” Simply said, it runs flat after being ruptured for a short period.

#4. Wheel Diameter

In inches, the wheel diameter is a two-digit value that represents the diameter of the wheel. 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. It denotes how much weight a tire can hold based on a conventional tire chart.

#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 more excellent speed rating can withstand more heat. As the speed rating increases, so does the construction quality and tire durability. A high rating, in some ways, 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, and 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 divided by 100, which gives you the sidewall height in millimeters, then divide that by 25.4 to convert it to an inch. The overall diameter is then calculated by multiplying the wheel diameter by two sidewall measures and then dividing 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, adequate wet and dry grip, increased winter traction, however not suitable in summer drive, a comfortable drive, and extended tread life.

Performance

These emphasize quick-handling, improved wet and dry grip, adequate winter traction, a sporty quality, and more pointed tread life.

All-terrain

Engineered for daring, with exceptional off-road traction, but louder and firmer on surface streets. Winter traction is adequate, and the wear life is sufficient.

Winter

Winter ones are specialists in snow, sleet, and ice grip and are designed to drive in low temperatures.

Track

These are for the racetrack, autocross, or drag strip, and the tires have incredible track performance, agile handling, and short wear life. Some are appropriate for usage on the street.

Special service

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

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