How to find out what is the diameter of the wheels on a bicycle

Bicycle wheel diameter

Many people when cycling do not attach much importance to self-service transport. Questions such as changing sprockets, lacing or repairing a tire are quite complicated in action, and there is a desire to learn a little more about the iron horse, and sometimes completely assemble a bicycle with your own hands. The latter option will make transport as convenient as possible, ride comfortable and take into account all individual characteristics.

When choosing a bike, no matter what type and for what age category, you need to pay attention to the wheel diameter. This parameter is usually measured in English inches and is indicated on the side of the tire. For each category of two-wheeled vehicles, there are certain dimensional parameters. One important thing to remember: the diameter of a bicycle wheel depends on the diameter of the rim and the thickness of the bicycle tire. Thus, you can choose the optimal type of equipment that will be comfortable to ride.

There are 7 of the most popular wheel sizes. For easy systematization, it is best to place the diameter types in the table. This will make the perception of data more convenient and correct. How to determine the size of a bicycle wheel?

Wheels 27, 28 and 29 have the same rim parameters, the difference lies in the thickness of the tire. Size affects many qualities of a technique, but there is no definite opinion on this matter. Physically speaking, if the wheel size is large, then a long distance will be covered, but it will take a lot of effort. Thus, the acceleration time is increased. A bike with small wheels is easier to speed up than the opposite option.

Children bicycle

In order for the child to ride comfortably and to learn how to control transport faster, it is necessary to select the correct wheel parameters. The data in the table below allows you to understand which age is best for which size is best.

Bicycle Wheel Selection. Size Chart

find, diameter, wheels, bicycle

The wheel is the most important part of the bike. When choosing it, you should rely on two parameters: weight and size. And if the weight is easy to determine. what is easier is better, then when choosing a size, the cyclist may be puzzled, because this characteristic directly depends on the scope of the bike. To simplify this task, experts have compiled tables with bicycle wheel sizes and implemented a traditional marking system. We will tell about them.

Bicycle tire markings

As mentioned above, in the classic version, the marking is applied to the side surface of the tire in the following sequence:

  • Diameter in inches.
  • Width in inches.

The standard marking looks like 20 / 1.75.

In the case of ISO marking, the sequence looks different:

  • Profile height in millimeters.
  • Rim diameter in millimeters.

The same wheel will look like 44.4 / 406.

For successful operation of the bike, use only tires and tubes recommended by the manufacturer. The fact is that tires that are overly narrowed from the normal size are prone to more frequent punctures, and too high a profile will provide noticeable resistance when driving and be damaged more often. Use only the correct tire sizes and enjoy a pleasant bike ride.


Today, the popularity of cycling has increased dramatically, this is due to the fact that people have begun to pay more attention to their health. Many experienced cyclists know everything from “a” to “z” in this business, but beginners sometimes do not even know what their wheel diameter is. Next, we will talk about how to measure the diameter of a bicycle wheel and how to measure the size of the frame.


Before answering the question of how to measure the diameter of a bicycle wheel, let’s talk a little about the wheels themselves, their dimensions, whether the speed of the bicycle depends on the diameter of the wheels.

A bicycle usually has two wheels. As a rule, bicycles use spoke wheels with steel spokes, there can be from 12 to 42, but, as a rule, there are 32 or 36.

Some sports bicycles are fitted with 4-6 pairs of flat carbon fiber spokes. Disc wheels are used, most often for cycling, have the greatest rigidity and aerodynamics.

The wheels, along with the frame, are the most important structural elements of a bicycle, it is the wheels that withstand all the load created by the cyclist. Also, the wheel must withstand all shock loads that occur with unevenness on the road.

Modern wheels are both very strong and lightweight at the same time. A wheel usually consists of spokes, a hub, a tube with a tire, a rim.

The size of the wheel is of great importance, with large wheels you can reach higher speeds, and with small ones, the bike is more compact. The smallest 20 “wheels are used in folding models, 26″ wheels are most often used for mountain bikes, and the largest 28 “wheels are common for road bikes.

Now, after all, let’s answer the question, how to measure the diameter of a bicycle wheel? And this is easy to do. The size from the highest point of the wheel to the lowest point will be the diameter of the bicycle wheel.


The size of the bike frame is selected based not on the height of the cyclist, but on the length of his legs, so you first need to know how to measure the size of the bike frame so as not to become a “victim” of the wrong purchase.

The bike frame is the main body to which the bike components attach. A bicycle frame is usually welded from profiles that form two so-called triangles. the front axle and the rear axle.

The bicycle frame is selected solely on the basis of the capabilities of both the material and physical data of the cyclist, as well as on what you are going to do on this bike, just ride in the park or on the slopes of the mountains, or can jump from high slopes and steep jumps.

Still, how do you measure the size of a bike frame? If you decide to buy a sports bike, then you need to stand on a flat floor without shoes and measure the height of your crotch, a tape measure will help you with this, multiply this figure by a factor of 0.665. for sports or road bikes.

And those who buy a bike for aggressive riding on hills and slopes, that is, a mountain bike, then multiply your figure by the coefficient for mountain bikes. this is 0.226, as a rule, mountain values ​​go in inches, the resulting figure must be multiplied by 2.54 and then we get the size in inches.

Methods for measuring wheel diameter

The very essence of measurement comes down to obtaining numerical data. centimeters, millimeters or inches. It can be done in several ways:

  • measure the radius;
  • ISO;
  • through the circumference.

The easiest is the first way. We take a centimeter or tape measure and place the bike vertically so that it does not fall. Place the zero straight edge on the hub axle and hold it to the edge of the tire. This will be the radius of the wheel in centimeters. Then we multiply by two. we get the diameter. To get millimeters, you need to multiply by 10, and inches by 2.54.

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ISO will measure the diameter and rim and height of the tire profile. This method may be necessary if you need to put a tire of a different profile. several types of tires can be selected for the same rim diameter.

Only measure the distance from the center of the hub to the outer edge of the rim. Knowing the radius, we multiply it by 200. we get the diameter in millimeters. And on it we select another tire.

The third method shows how to determine the diameter in terms of the circumference. For these purposes, you will need a cable and a tape measure. We wrap the tire with a cable, make a mark at the junction with the beginning of the cable. We straighten and use a ruler to measure the distance from the beginning of the cable to the mark. This will be the circumference.

  • Apply a staple mark of paint to the tire.
  • Place the wheel so that the mark is in the lowest position.
  • Ride one turn.
  • At the bottom, the paint will be erased from the tire, and on the sides it will remain, you can understand that the wheel was rolled exactly the opposite.
  • Measure the length of the dyed mowing line.

Do not be afraid that for large wheels this value will exceed 200 cm. First, divide it by 3.14. we get the diameter in centimeters. And then divide by 2.54 to convert to inches. Actually, it’s so easy to find out what size the wheel of a bicycle is.

When measuring with a ruler, you will most likely get fractional values, for example, 28.23 inches. Round up to whole values, taking into account the existing diameters.

What are the sizes of bicycle wheels?

The geometric parameters of bicycles differ according to a strict pattern. this also applies to the size of the frame and the diameters of the wheels. First, let’s present a size chart:

Wheel, inches / mm Rim, mm Bicycle
20/508 406 Children’s, teenage, folding, BMX
24/609 507 Teenage, foldable adult
26/660 559 Mountain
28/711 622 Road, hybrid, highway
29/736 622 Mountain niner

The first column shows the traditional wheel diameters in inches and millimeters. The wheel is measured with the tire. To find out the size of the rim, you need to subtract the height of the tire, multiplied by two. Standard rim sizes are shown in the second column.

Bicycle wheel measurement systems:

  • classic, in inches;
  • in centimeters;
  • ISO standard, in millimeters.

The International Organization for Standardization (ISO) has implemented a universal wheel measurement system to avoid confusion. All bicycle manufacturers adhere to it. The dimensions of the wheels are made up of the diameter of the “clean” rim and the width of the tire profile.

When choosing new tires, you need to know the rim landing diameters. these numbers on the tires must correspond to them. This will come in handy when changing to a different tire profile. In everyday life, a wheel is measured in inches, and it is more convenient to give dimensions in inches. And by the size of the wheel, you can also determine the type of bike. walking, mountain or road.

Wheel sizes are important to know when choosing a child’s bike. There is a direct relationship between the numerical values ​​of the diameters with the height and age of the child, the so-called “wheel size”. Below is a table of standards:

Diameter, inches Height, cm Age
12 up to 98 3
fourteen 98. 104 3. 5
14, 16 104. 110 4. 5
16, 18 110. 116 5. 6
twenty 116. 128 6. 8
24 up to 164 over 8

Wheel sizes for kids ‘bikes are separate from adults: kids’ range ends on 24 “wheels, while for adults it just starts (excluding 20” BMX). 24-inch wheels can be safely attributed to teenage and universal (for small adults). Of course, this data will only help you choose a bike, otherwise you need to try it on.

How to measure the diameter of a bicycle wheel

Sooner or later, the cyclist is faced with such a concept as the size of the wheels. This may be already at the time of buying the bike or the first time you replace the punctured tube and tire. How important is it to know the geometric parameters of the “running” bike? Nothing less than going over the bushing or lubricating the chain.

Determining the diameter of a bicycle wheel is very simple. We will talk about this in our article. Of course, this parameter is most likely to be recognized precisely from the moment of purchase or in the process of “studying” their two-wheeled friend. Nevertheless, suddenly he is unknown for some reason, for example, they gave him a ride for a while, and then the tire went flat, and it is necessary to put a new camera.

Bicycle tire markings

And now a little about tires and their meanings. According to the classical system, the dimensions are applied in the following order: wheel diameter in inches / tire profile width.

According to the international ISO system, the same parameters are stuffed onto rubber in the opposite order. first the profile height, then the rim landing diameter. Values ​​are in millimeters. For the same tire or tube 20 / 1.75 in ISO it will look like this: 44.4 / 406.

The table below shows the ranges of the profile heights of tires for the landing diameters of the rim:

Standard markings Rim, mm
20 / 1.5. 2.125 406
24 / 1.5. 2.125 507
26/1. 2.35 559
27/1. 1.75 622
28/1. 175 622
29 / 1.75. 2.35 622

The listed tires can be selected for one fit size. However, it is better to take into account the recommendations of the bike manufacturer in the passport and adhere to the recommended parameters. Tires that are too narrow will puncture more often, while tires that are too high increase resistance to movement and can damage the sides. Each rim has its own tires. Optimum matching of tires to wheel sizes will allow you to ride longer, without punctures or damage.

Measuring the tire in the usual way

    Place your bike upright by leaning it against a wall or on a stand. When the bike is positioned strictly upright, it does not lean on you, and it is easier to measure its wheel. If you are measuring the wheel alone, it is better to use a metal tape measure rather than a plastic one, as this can be done with one hand.

Measure the distance in inches from the ground to the center of the wheel. This will measure the radius of the wheel or half the diameter. Multiply this length by two to calculate the tire diameter. Except for BMX models, most adult bicycle wheels are 26 to 29 inches in diameter.

Measure the distance from one side of the tread to the other. This number is the width of the tread. It can vary greatly, depending on the destination. Generally, the wider the tread, the higher the flotation, while the narrower tread is used for a smooth and fast ride.

  • When buying a new tire, remember that in traditional standard sizes, diameter comes first, then width. For example, a 26 x 1.75 tire will have a 26 “diameter and 1.75” tread width.
  • Tire measurement using the ISO method

      Find out if your tires are measured using the ISO system instead of the conventional method. The ISO system uses millimeters to determine the dimensions of a bicycle wheel. If you do not have a tape measure to measure a wheel in inches, just know that there are 25.4 millimeters in one inch and use a calculator to multiply the width by 25.4.

    Make sure the bike is placed against a wall or on a stand. Measure in millimeters from the center of the wheel to the inner edge of the tire. Double this number to calculate the diameter. Most ISO-measured adult bicycle tires are 650 to 700 millimeters in diameter.

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    Measure the tire width in millimeters. Use the recommendations above for measuring the tread. Remember that tires of different widths can be used on the same bike as long as the difference is not too drastic.

  • When buying a new ISO-measured tire, remember that width comes first, followed by diameter. For example, a bicycle wheel measuring 53.3 x 700 has a tread width of 53.3 mm and 700 mm in diameter along the inner edge of the tire.
  • How to measure a bicycle wheel

    To purchase a spare tire for a bicycle, you must first determine the size of the wheel. In fact, measuring a wheel is a common procedure during bicycle maintenance.

    Bicycle wheel measurements can be done in two ways, including tire and rim sizing, and both are simple to perform. Sometimes it is necessary to know the circumference of the wheel, which is also not difficult and can be done in several ways.

    Calculating the circumference of a bicycle wheel

      Measure the circumference, or distance, along the outer edge of a bicycle wheel, in order to more accurately adjust the speedometer, odometer, GPS or bike computer. If you recently purchased a cyclometer or you need to adjust an existing one because you have installed tires with a different tread size, you need to determine the wheel circumference.

    Calculating the circumference is easy by multiplying the tire diameter by pi. The circumference can be quickly determined if you already know the outer diameter of the tire. Since pi is 3.14, the circumference of a 26 “tire can be obtained by multiplying 26 by 3.14, which equals 81.64”. If you already know the tire diameter and tread width, the circumference can be found on the Internet.

    Measuring the circumference with a rope. If you do not know the diameter of the wheel, you can measure the circumference by gently running a string around the outer edge of the tire. Mark or cut the thread where it reaches the starting point and measure its length to determine the tire circumference.

  • Place a dot of paint on the tire tread. Carefully roll your bike on a straight line with the mowing line so that the wheel makes two turns and the paint marks are visible twice on the ground. Measure the distance from one spot to another to determine the circumference.
  • Bicycle wheel markings

    For an ordinary user, it is enough to visually look at the size of the bicycle wheels to make a decision to buy a vehicle, but sooner or later, the desire to understand the wheel markings will prevail. So what can you learn by reading the symbols on the wheels of a bicycle?

    Manufacturer. Of course, the brand of the manufacturer is written in large letters on any wheels, which, over a long period of operation of the wheels, is an advertising platform.

    Tire size. As a rule, ETRTO standards are taken as a basis. On the tire it is written in numbers 52-559, and 2.0026 in brackets. The first numbers are the inner and outer diameters in millimeters, and the size in inches is indicated in parentheses.

    Pressure. The pressure to which the wheels can be inflated is written in small numbers and letters along the inner radius of the wheels. Measurements are written in different units of measurement (most often. Atmospheres (Atm), Bar and PSI), from the minimum to the maximum indicator.

    Direction of movement. This parameter is also very important, since the design features of tires are designed for certain physical loads and if installed incorrectly, tire wear will occur many times faster.

    In order not to be mistaken, the direction of movement is usually indicated on the tires in the form of an arrow.

    And, of course, important information is the date of production of the tire. These numbers can not be found on all wheels, but the most conscientious manufacturers will definitely indicate the “freshness” of the product.

    Children’s rim sizes (12-20)

    The 12th size is put on children’s bicycles for the smallest. from 2 years old. As a rule, these are either three-wheeled or two-wheeled with auxiliary plastic wheels.

    Size 16 is designed for bicycles for older kids. 4-7 years old.

    19-th size refers to children only conditionally. This is a specific size that is most often set on models for trial cycling (overcoming obstacles and jumping on bicycles). Such a small size of the wheel is due to the fact that in this case speed is not as important as the lightness of the vehicle.

    Size 20 (rim diameter. 406 mm) is the boundary, since it simultaneously refers to the last child and the first adult. Most often it is referred to as adolescent. Many bicycle trial “iron horses”, along with the nineteenth size, are equipped with the twentieth, as the more common and affordable tires. As a rule, these rims are also found on folding bicycles.

    Selection procedure

    Professionals recommend paying attention to a few points before choosing a bicycle rim:

    Record the amount of money you can spend on rims and weigh your riding style soberly. A choice will be made depending on it. Is the appearance important, whether it is jumping or serious punches

    Note the double aluminum rims. They are versatile, lightweight and inexpensive.

    If the distances are large, pay attention to the weight, but the strength should be relegated to the background. field repairs once a season are quickly compensated for by the absence of a loss of 2-5% of speed. Pay attention to tubeless wheels. At a high price, they provide very great convenience in terms of the almost complete absence of punctures. For jumps and asphalt, wide rims are good, although it’s better not to go on the track with them.

    Below we will reveal some of these tips and make a short introduction to the terms and features.

    1 Stand the bike upright against a wall or on a stand. jpg a Bicycle Wheel Step 1.360p.mp4

    2 Measure the distance from the point where the tire touches the ground to the point where the rubber tire enters the metal rim. The resulting distance will be the thickness of the tire. jpg a Bicycle Wheel Step 2.360p.mp4

    3 Multiply this value by 2 because the tire covers the wheel from all sides, top and bottom. jpg a Bicycle Wheel Step 3.360p.mp4

    4 Measure the diameter of the wheel rim. jpg a Bicycle Wheel Step 4.360p.mp4

    5 Add the rim diameter to the tire thickness you multiplied by 2. This adds up to the wheel size. jpg a Bicycle Wheel Step 5.360p.mp4

    How to find out the size of a bicycle wheel?

    To correctly determine the size of a bicycle wheel, you must take into account that the measurement is made in English inches and is denoted by “”.

    Today there are the following basic sizes of bicycle wheels:

    • twenty”. Children’s bicycles or those models that can be folded.
    • 24 “. Teenage and stunt models.
    • 26 “. This standard is the most widely used. Wheels of this size are installed on mountain and walking models.
    • 27 “. Medium road bikes.
    • 27.5 “. Extreme mountain bikes.
    • 28 “and 29”. This standard is applicable to mountain and hybrid models.
    • 36 “. Bicycles with such wheels easily overcome stones, mud and other road imperfections.

    When choosing the size of bicycle wheels, most often buyers give their preference to 26-29 inch models. When it comes to a child or teenager, it is better to consider wheels 20 and 24 inches.

    A bicycle with tires 68cm in diameter travels 7.2 km. How many revolutions do the wheels make?

    How to find out the diameter of a bicycle wheel?

    Measuring the diameter of bicycle wheels can be done in the following ways:

    • Radius measurement.
    • ISO method.
    • Circumference measurement.

    The easiest way is to use the first method. The tape is drawn to the edge of the tire from the very beginning of the hub axis. The resulting figure is doubled. To convert a digit to inches, the number is multiplied by 2.54.

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    How to determine the ISO size of a bicycle wheel? The rim and profile diameters are measured here. This definition is the most accurate if you need to install a tire of a different profile. Consequently, the same rim diameter allows for a selection of different tires.

    How to find out the size of a bicycle wheel?

    If it becomes necessary to replace a punctured tire or purchase a spare bicycle tire, you first need to determine the size of the wheel. For this, it is important to know how this indicator is measured correctly. Taking into account all the nuances, finding the size of the tire seems to be a fairly simple task.

    What diameter of bicycle wheels to choose?

    The differences between the permissible wheel diameters are obvious. When choosing a size, first of all, you need to rely on the type of bike and the personal preferences of the owner:

    • Bicycles with 29 “wheels are excellent obstacle course and are easy to handle. But, if you compare them with the 26 “models, additional physical efforts may be required to develop high speed here.
    • 26 “wheels are more agile, pick up speed and stop quickly. But, if we consider inertia, the primacy is undoubtedly given to 29 “models.
    • What diameter of bicycle wheels should a child choose? Only 20 “and 24” wheels are considered here. Such cycling will not require a significant expenditure of energy and will be perfectly combined with the small growth of the baby.

    Bicycle wheel sizes

    To begin with, so as not to get confused, let’s start using the British-American inch system, which is most familiar today.

    Depending on the outer diameter of the wheel (in inches), they can be conditionally divided into groups corresponding to the type of bicycles:

    • 10 ″, 12 ″, 14 ″, 16 ″. for children’s bicycles;
    • 18 ″, 20 ″. for teenage bicycles, compact folding city bikes;
    • 24 ″. for teenage bikes, compact folding city bikes, stunt BMX bikes;
    • 26 ″ for teenage bikes, full-size city bikes, obsolete MTB size;
    • 27 ″. classic size for racing road;
    • 27.5 ″. a new universal (so-called “French”) size gaining popularity for sports (mountain bikes, road bikes, cycling hybrids, trekking) and road (work), city, walking, touring bicycles;
    • 28 ″. old (but not aging) universal size for sports bike hybrids, as well as road (work), city, walking, touring bicycles;
    • 29 ″. for a special type of mountain MTV. “niners”;
    • 36 ″. the newest experimental size, which is just “groping” its place in the cycling world.

    Typology of bicycle wheels depending on the tire width:

    • 18mm to 25mm, or up to 1 “(13mm rim). Narrowest for racing road bikes;
    • 23mm to 32mm, or 1 ″ to 1.25 ″ (15mm rim) Medium-narrow for cyclocross bikes;
    • from 25mm to 37mm, or from 1 “to 1.5” (on 17mm rim). mid-size, for road, city, pleasure bicycles;
    • from 28mm to 44mm, or from 1.1 “to 1.75” (on 19mm rim). medium-wide, for touring (tourist);
    • 28mm to 47mm or 1.1 “to 2” (on 20mm rim). medium-wide, for MTV cross-country, bicycle hybrids, trekking bikes;
    • from 40mm to 50mm (1.5 “- 2.1”) on a 23mm rim or from 44mm to 57mm (1.75 “- 2.25”) on a 25mm rim. wide, for MTB and BMX used in extreme disciplines;
    • from 75mm (from 3 ″) and more (on a rim of 32mm or more). extra wide, for all-terrain fetbikes.

    What is the size of a bicycle wheel?

    First of all, let’s clearly understand that the size of a bicycle wheel has two main parameters:

    • diameter, which is the sum of the rim landing diameter and twice the tire height;
    • width, which is determined by the width of the bike tire. The width of the wheel rim, which is always less than the width of the tire, is not decisive in this case, and is only important when selecting a tire for the existing rim.

    In the concept of size, a common understanding of the unit of measurement is important. Quite often, the size of bicycle wheels is given in inches (US. British sizing system). But no less common is the old metric (so-called “French”) system of sizes. Recently, the new standardized metric system ISO is gaining more and more popularity.

    Bicycle tire labeling options

    The size designation of the bicycle tire is displayed on the markings applied to the product. The designation is applied in accordance with the manufacturer’s standard. Possible options:

    • ISO marking (ETRO), example. 37-622, where 37. tire width in mm, 622. landing diameter in mm; lack of marking. it is impossible to immediately determine the outer diameter (circumference);
    • three numbers (in inches), example 28 × 1 5/8 × 1 3/8, where 28 is the outer diameter, 15/8 is the height, and 1 3/8 is the width of the tire;
    • two numbers (in inches), example 28 × 1 3/8, where 28 is the outer diameter, and 1 3/8 is the width of the tire, does not allow to determine the exact value of the landing diameter on the fly;
    • French standard, example 700 × 35C, where 700mm is the outer diameter, 35mm is the width of the tire, letter C indicates the landing diameter of 622mm.

    Thus, in all standards for marking a bicycle wheel, except for the ISO standard (ETRO), the outer diameter of the wheel, it is also its true size, is taken out in the first figure (in inches, or in millimeters). For the ISO standard (ETRO), the outer diameter of the wheel is found by decoding.

    How to find out the wheel size

    Here, they tell the cyclist. here you need to install a 24-inch wheel, here. pick up a 26-inch wheel, and here. a 28-inch wheel. But no matter how you twist this wheel, nowhere on it is its size explicitly spelled out. The wheel rim has its own marking, the tire has its own. How to find out, determine, measure the size (diameter or width) of a wheel on a bicycle?

    Methods for determining the size of a bicycle wheel

    Methods for determining the size of a bicycle wheel include:

    • by decoding the marking on the bicycle tire, primarily because the marking on the bicycle tire already contains the parameters of the rim on which it is installed. Deciphering the factory markings on a bicycle tire is the most reliable way to determine the true size of a bicycle wheel and gives the most accurate results.
    • by the method of full-scale measurements, using a ruler, caliper or tape measure. It can be measured either with a metric ruler, with the translation of the measurement result into inches (D or 2R in cm divided by 2.54), or with a ruler (tape measure) with an inch scale. The width of the wheel (tire) is best measured with a caliper. The method of full-scale measurements using a hand-held measuring tool is less reliable, since it depends on the human factor and possible errors. So, for example, when measuring the diameter of wheels of 27 inches and 27.5 inches, it is quite possible to make an error of 0.5 inches, and when measuring the width of the rim, make a mistake by only 1 mm, and incorrectly determine their size.

    Decoding the size of the bicycle through its marking

    This summary table of standard sizes of bicycle tires (which determine the dimensions of the bicycle as a whole) allows you to compare the standards for their designation (marking) with each other, and determine the true dimensions (outer diameter and width) both in inches and millimeters.

    Summary table of standard bike tire sizes

    Natural inches (outer diameter and width)

    How to measure your wheel circumference

    Inches decimal (outer diameter and width)