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Bike Wheel Sizes Explained

With so many bike wheel sizes available, figuring out which bicycle wheel size you need can be a real head-scratcher.

Which size bike wheel do I need? What size are my current bike wheels and what do the different bike wheel sizes even mean?

Knowing of the confusion wheel sizes can cause, we threw together this short yet comprehensive guide to answer all of your bicycle-wheel-size-related questions.

If you’re unsure what size your bike wheels/tires are and want a quick & accurate way to measure them, read our step-by-step guide.

If you’re looking for a bike wheel size chart, this article contains several, including one with ISO (International Standardisation Organisation) measurements. 

Bike Wheel Size Guide

At the top of the wheel size guide, I start by explaining kid’s bike wheel sizes and later in the article, I’ll talk you through Adult/standard bike wheel sizes

You can use the table of contents below to jump to a section you want to learn more about. Otherwise, let’s get straight into it!

Table of Contents
    Add a header to begin generating the table of contents

    Bike Wheel & Tire Units of Measurement Explained

    It’d be ideal if a single unit of measurement were used to help size bike wheels, but unfortunately, the cycling industry has many illogical twists and turns. 

    Several countries have their own units of measurement for bicycle tires and wheels. This means it’s essential that you understand the standard sizing systems so that you won’t struggle to order new inner tubes or tires when the time comes. 

    The main wheel sizing systems are as follows:

    Bike Wheel Size Chart
    Whilst French sizes originally described the width of a wheel, the lettering used by French wheels sizes is much less common nowadays.

    ETRTO (European Tire and Rim Technical Organization) is a modern system used to distinguish different-sized bike tires and rims. 

    In recent years, the ISO wheel sizing method has adopted the ETRTO system, and is now known as the ERTO and is the same as the ISO wheel and tire size measurement.

    ERTO is a measurement of wheel circumference introduced to attempt to help make sense of the many wheel and tire sizes available. 

    The International Standardization Organization was created on February 23rd, 1947, to combine and formulate various international measurements into a single measurement that can be used and understood worldwide. 

    Standardisation of bicycle wheel sizes has been warmly welcomed by many cyclists as it’s beneficial when combining bicycle parts from different countries.

    The ISO name that defines the ETRO standard is ISO 5775. 

    The ISO sizing system uses two numbers. For example, a typical ISO tire size for road bikes is 662 x 25c (700 x 25c).

    The first number represents the width of the tire or rim in millimetres.

    The rim’s width is measured across the bead seat section on the side of the rim wall. This distance is referred to as bead width. A tire’s width is measured when it’s inflated.

    The second number in the ISO system is the BSD or bead seat diameter.

    This measurement is taken in millimetres and represents the diameter or distance between the bead seats on opposite sides of the rim.

    ISO and ETRTO wheel measurements - 700C to inches explained

    The “700” found on many bike tires represents the rough diameter of the bike wheel across the width of the tire.

    The JIS serve a similar role in Japan to the ISO.

    The JSO sets standards for industrial services in Japan and is Japan’s member body of the ISO.

    The JIS standard for bicycle rims is JIS D 9421, and the corresponding ISO standard for this is ISO 5775-2:1996.

    After the introduction of the ISO wheel sizes, French wheel size usage has slowly declined.

    The French system ranges from A to D. Tires labelled with A are narrower, and D are wide

    Many wheels and tires still display part of the French tire size system. For example, the “C” found on most 700C road bike wheels represented a wide tire.

    Contrary to popular belief, “c” on a bike wheel size does not stand for centimetres!

    The letters from the French tire sizing system no longer correspond to tire width, as tires of varying widths are now made for the same wheel sizes. 

    Old English and American tire sizes are fortunately not as popular as they used to be as they’re ambiguous and frequently cause confusion.

    English/American tire sizes are generally referred to as fractional tire sizes and display tire sizes in inches and fractions. Confusing, right?! 

    26 x 1 3/8 EA3 is a standard fractional tire size. Translated to ISO, this tire would be 37 x 590.

    The “26” represents the tire’s diameter when inflated, and the “1 3/8” represents the tire’s width. 

    Bike Rim Wheel and Tire Sizes

    How to Locate Bike Tire & Wheel Sizes

    Fortunately, if you still have tires on your wheels, it’s super easy to find out what tire size you need. 

    If you don’t have tires on your wheels, I’ve put together a separate guide that teaches you how to measure bike wheel size for tires, have a read. 

    Finding your bicycle tire and wheel size is as easy as reading the printed measurements on the tire and rim wall. 

    The picture below displays these markings on the tire and rim of a mountain bike. 

    As you can see, you’ll always find an ISO measurement alongside the ERTO, and from time to time, on older bikes and tires (and some mountain bikes), you might find a fractional wheel size. 

    How to read a bike wheel measurement
    Tire wall reads "40-622, 28 x 1.50, 700 x 38c"

    Now that you’ve discovered your bike wheel size and tire size, it’s time to learn about the standard wheel sizes and what each size is suitable for. 

    Towards the end of either section, you’ll find a kids’ and adults’ bike wheel size chart, which will help you identify and understand different tire and wheel sizes. 

    Sometimes worn and old tires can be tough to read. If you could find a size on your bike tires, read my guide, which will teach you the fastest way to measure bike wheels and tires

    Bike Wheel Sizes Explained

    Let’s take a look at the different bike wheel sizes of both kid’s and adult’s bikes. 

    The kid’s wheel size info begins just below; if you need the adult wheel size information, click here.

    Kids Bike Wheel Sizes & Other Small Bike Wheels

    Unlike adults’ bikes, kids’ bikes are measured by the size of their wheels. Below I explain some of the most common wheel sizes for kids’ bikes.  

    If you want to find out about the different kids’ bike wheel sizes and how to accurately measure and size a bike for a child, you’ll want to read my Kids’ Bike Size Guide.

    Kids’ bikes with 12-inch wheels are designed for children between the ages of two and four. 

    Most bikes with 12″ wheels won’t have any pedals, these are known as balance or training bikes. Balance bikes are great for younger children who are getting to grips with riding on two wheels and learning to balance.

    12″ bike wheels have a BSD (bead seat diameter) of 203mm and are accompanied by a wide range of tires, from off-road inclined tires with chunky tread to slicker road-inclined tires. 

    Bear in mind that if your child is taller than average, a 14″ or 16″ bike may be better suited to them.

    14″ kids bike wheels are designed for children between the age of 5 and 6. Three to four-year-old kids that are taller or bigger than average may also find a 14″ kids bike more suited to their body proportions. 

    14-inch bike wheels can vary slightly in size, which means there are several different ISO measurements that you might come across when looking for a 14″ wheel or tire.

    As stated above,  14″ wheels have e a standard ISO of 298m, but several other sizes are available, ranging from 254 to 298mm. This range of sizes means you must know what ISO size your bike wheel fits before purchasing new wheels/tires (read this guide for help).

    Kids’ bikes with 16″ wheels are suitable for children between the ages of five and six. However, depending on your child’s height, they may require a 14″ bike if they’re smaller or an 18″ bike if they’re taller than average. 

    16″ wheels have a standard ISO size of 305, but different sizes are available that range from 305 to 349mm.

    A wide range of 16″ ISO sizes means buying the right tires for your 16-inch wheels can be challenging.

    This guide teaches you the easiest way to take an ISO measurement for all wheel types.

    Outside of kid’s bikes, 16″ wheels are also used by many folding bikes, including the Brompton bike range and by several recumbent bikes and trikes as the front wheel.

    18″ bike wheels are designed for kids’ bikes and BMX riders who aren’t yet ready for a full-size 20″ BMX.

    Like all wheels, 18″ bike wheels come in varying sizes, so their BSD measurement can range from 355 to 400mm, but their standard BSD is 355mm.

    Kids between the ages of seven and nine are most suited to 18″ wheels. However, if your child is shorter or taller than average, they may require 16 or 20-inch wheels.

    20-inch bike wheels are an excellent option for children between the ages of seven and nine. 

    As you can imagine, due to their reduced size, 20-inch wheels are typically found on kid’s bikes, but they’re also the size of BMX bike wheels. 

    Like most bike wheels, 20-inchers vary slightly in size, with their BSD (bead seat diameter) ranging from 400 to 451 mm. However, 20-inch wheels with a BSD of 406 mm are most common.

    Make sure to measure your 20″ wheels before purchasing new tires to double-check you’re buying the correct size. Learn how to measure BSD here.

    24″ bike wheels are used by bikes designed for children between the ages of 10 & 11 years. 

    If your child is shorter than average, they may require 20″ wheels, or if they’re taller than average, they may be ready to graduate to a full-size adult bike. 

    24-inch bike wheels have varying bead seat diameters, ranging from 507 – 541mm. Make sure to take a reading of your 24″ wheels before buying new tires, or check the tire wall to find the right size for your replacement tires!

    a table providing accurate bike wheel sizes for children of different heights and ages
    For more precise sizing, use the tables below

    Kids Bike Wheel Size Charts - Age, Inseam Height & Sex

    Below as promised, you’ll find three different kid’s bike wheel size charts.

    Again, these are for kids’ wheel sizes, so if you’re looking for adult bike wheel size charts, click here

    Otherwise, choose your preferred table and calculate the most suitable wheel size for your child.

    Kids Bike Wheel Size Chart - Height & Inseam

    Rider Height Inseam (Inches) Suggested Kids Bike Wheel Size
    2'10" - 3'4" 86cm - 101cm 14" - 17" 35cm - 42cm 12" Wheels
    3'1" - 3'7" 94cm - 109cm 16" - 20" 40cm - 50cm 14" Wheels
    3'7" - 4'0" 109cm - 122cm 18" - 22" 45cm - 55cm 16" Wheels
    3'9" - 4'3" 114cm - 130cm 20" - 24" 50cm - 60cm 18" Wheels
    4'3" - 4'5" 122cm - 135cm 22" - 25" 55cm - 63cm 20" Wheels
    4'5" - 4'9" 135cm - 145cm 24" - 28" 60cm - 72cm 24" Wheels
    >4'9" >145cm >28" >72cm 26", 27.5" & 700c Wheels (adult bikes)

    Kids Bicycle Wheel Size Chart - Sex, Age & Height

    Boys Bike Wheel Size Guide

    The bike wheel size chart below is for boys between 2-12 years old. 

    Once Boys are 12 years old, they’ll generally require a full-size adult bike. But, depending on how quickly they grow, some may need one sooner or later than the age of 12.

    You’ll find the bike wheel size chart for girls here.

    Rider Age Rider Height Suggested Boys Bike WheelSize
    2 years old 34.2" (86.8 cm) 12 inch wheels
    3 years old 37.5" (95.2 cm) 12 inch wheels
    4 years old 40.3" (102.3 cm) 12 inch wheels
    5 years old 43.0" (109.2 cm) 14 to 16" wheels
    6 years old 45.5" (115.5 cm) 14 to 16" wheels
    7 years old 48.0" (121.9 cm) 18 to 20" wheels
    8 years old 50.4" (128 cm) 18 to 20" wheels
    9 years old 52.5" (133.3 cm) 18 to 20" wheels
    10 years old 54.5" (138.4 cm) 24" wheels
    11 years old 56.5" (143.5 cm) 24" wheels
    12 years old 58.7" (149.1 cm) 26", 27.5" & 700c Wheels (adult bikes)
    Girls Bicycle Wheel Size Guide - Age & Sex

    Here’s the girl’s bike size chart for those between 2 and 12 years old. 

    Like boys, once girls are 12 years old, they’ll require a bike with full-size wheels. 

    This girls’ bike wheel size chart uses average age to height data, so if your child is above or below average height for their age, it may be worth test riding a few different sized bikes at your local bicycle shop.

    Rider Age Rider Height Suggested Girls Bike Wheel Size
    2 years old 33.7" (85.5cm) 12 inch wheels
    3 years old 37" (94cm) 12 inch wheels
    4 years old 39.5" (100.3cm) 12 inch wheels
    5 years old 42.5" (107.9cm) 14 to 16" wheels
    6 years old 45.5" (115.5cm) 14 to 16" wheels
    7 years old 47.7" (121.1cm) 18 to 20" wheels
    8 years old 50.5" (128.2cm) 18 to 20" wheels
    9 years old 52.5" (133.3 cm) 18 to 20" wheels
    10 years old 54.5" (138.4 cm) 24" wheels
    11 years old 56.7" (144cm) 24" wheels
    12 years old 59" (149.8cm) 26", 27.5" & 700c Wheels (adult bikes)

    Standard Full-Size Bike Wheels

    If you’re wondering what size bike you need or what mountain bike wheel size is best, you’ll find some interesting information in the sections below. 

    After the standard wheel size section, you’ll find some basic information on oversized wheels, followed by a bike wheel size chart which displays the different BSD (bead seat diameter) measurements available for varying sizes. 

    26-inch bike wheels are full-sized adult bike wheels.

    For a long time, 26-inch bike wheels have been the standard wheel size for mountain bikes and old American cruisers.

    During the early years of MTB, 26″ cruiser wheels were the only size capable of handling rough off-road terrain, which explains why they were the first and most common wheel size used by early and concept mountain bikes. 

    Whilst 27.5″ and 29″ MTBs are becoming more popular, 26″ wheels offer many benefits, such as increased strength and fast acceleration. 

    26-inch bike wheels are considered full-size, but they are slightly more suitable for shorter cyclists, who may struggle to reach the ground or steer on a 29er bike. 

    As with all wheel sizes, tires will vary slightly with 26″ wheels. Be sure to measure your BSD before buying new tires for your 26″ wheels as there are several wheels with differing BSD measurements ranging from 559 to 599mm.

    That said, 559 mm is the standard BSD size for 26″ wheels. 

    You’ll hardly find 27″ wheels anymore nowadays. 27-inch wheels were once used by road bikes that used an old style of derailleur. 

    On top of this, 27-inch bike wheels were also used by many American (70s and 80s) and Danish bike manufacturers. But like the retro road bikes, these 27ers are now much less common. 

    27-inch bike wheels can have a BSD measurement of between 609 and 630mm, but 630 mm is the standard for 27″ bike wheels.

    27-inch wheels aren’t used by modern bikes, so it’s slightly harder to find the right tires, but you’ll still find some manufacturers that produce tires for 27″ bike wheels. 

    27.5″ bike wheels are now one of the most popular bike wheel sizes. 

    As you just read, 27.5″ bicycle wheels are also sometimes referred to as 650b wheels.

    If you read the first section in this short bike wheel size guide, you’ll understand that the lettering found in several bike wheel sizes is a French system, originally used to indicate the width of the wheel. 

    650b wheels were originally used by French and some other European touring bikes as their width provided increased stability, strength and traction whilst riding off-road.

    In addition, these 27.5″ bike wheels have a standard BSD (bead seat diameter) of 584 mm. 

    Nowadays 650b wheels are used by tandem bikes, old European utility bikes and many mountain bikes. 27.5″ wheels offer several advantages compared to 26 and 29″ wheels. These advantages include:

    • 27.5-inch wheels offer a shallower attack angle than 26″ bike wheels, which makes crossing uneven terrain and large obstacles smoother.
    • 27.5″ bike wheels offer increased acceleration and manoeuvrability compared to 29-inch bike wheels, making them suitable for trails and rides where you’ll be taking on sharp corners.

    700, 700A, 700B and 700C are the four traditional 28″ bike wheel sizes.

    28-inch bike wheels were used by old English road and track bikes and several Asian and Middle Eastern countries (where these wheels are more popular now).

    Nowadays, 28″ bike wheels are found on road and mountain bikes. In fact, 28″, 700C and 29″ wheels all refer to the same rim size. These different sizes are used as marketing terms.

    700 and 700A wheels are uncommon now, but 700B wheels have an ISO of 635mm and are still used worldwide by several gravel and other off-road inclined bikes.  

    28-inch wheels that are 1 1/2 inches wide appear from time to time on older Dutch, English, Chinese and Indian rod-brake roadsters. 

    The standard BSD (bead seat diameter) measurement for 28″ bike wheels is 622 mm. Previously 28-inch bike wheels with a BSD of 647mm were popular, but these are no longer available. 

    Believe it or not, 29-inch and 700c wheels are the same size and are becoming more popular.

    Cyclocrossgravelhybrid and many mountain bikes are now equipped with 700c wheels for their high top-speed and larger surface contact area (meaning improved traction). 

    As you’ll probably know, virtually all road bikes also use 700c wheels nowadays as they provide an increased top rolling speed compared to smaller wheels and a smoother ride thanks to their decreased attack angle. 

    Some riders don’t enjoy that 29-inch wheels are less manoeuvrable than 26 or 27.5-inch  wheels, which is why until recently, they were only really found on road-inclined bicycles.

    Whilst both road and mountain bikes utilise 700c wheels, 29″ mountain bike rims are understandably wider, providing increased surface contact for more intense off-road sessions.

    Just like 28″ wheels, 700C wheels have a BSD of 622 mm. 29″, 29er, and 700C measurements are marketing terms used to describe the wheels of different bike types

    Road bike wheels are almost always referred to as 700C, whereas mountain bike manufacturers use the term 29-inch or 29er to describe their bikes. 

    Since it really varies upon the discipline of cycling, you’ll be riding and your preferred riding position & style, it’s not possible to give you an accurate mountain bike height-to-wheel size chart or the same for road bikes. 

    Below, you’ll find the table for road bike sizing; if you need the MTB size chart, you can view it here

    an easy to read Road Bike Size Chart calculated from rider inseam and rider height

    Click here to learn the most accurate ways to measure your inseam and height. Poorly taken measurements will lead to an inaccurate bike fit.  

    Bike Wheel Size Chart - ISO Sizes

    The table below contains the ISO sizes that apply to each wheel size.

    Several of these ISO sizes are no longer in production or are rare to find, so I’ve highlighted the most common ISO size for each wheel in bold.

    Wheel Size ISO Sizes Available
    26-Inch 559, 571, 584, 590, 597 mm
    27-Inch 609 & 630 mm
    27.5-Inch 584 mm
    28-Inch 622, 635, 642 mm
    29-Inch 622 mm

    Mountain Bike Wheel Size to Rider Height Chart

    Most road bikes use 622mm (700c or 29″) wheels, whereas mountain bike wheels vary depending on what MTB discipline you’re riding or how tall you are. 

    Smaller riders with shorter arms can struggle with steering on a 29er, while taller riders can find 26-inch MTBs too small.

    The table below displays approximate recommendations for each bike wheel size.

    If you’re unsure which wheel size will work best for you, the best thing to do is test ride several different MTBs and choose your preferred size. 

    Wheel Size Required Rider Height
    26-Inch > 4'10" (149 cm)
    27.5-Inch > 5'5" (165cm)
    28-Inch > 5'6" (168cm)
    29-Inch > 5'6" (168cm)

    Oversized Bike Wheels

    Plus-bikes or oversized bikes are for the tallest cyclists out there. 

    These bikes are typically made to order and will subsequently cost considerably more than a regular-sized bike. 

    Shaquille O’Neal is a perfect example of someone who requires an oversized bike. He’s 7′ tall (2.16m) and rides a 36″ bike made by Dirty Sixer.

    Otherwise, TrueBike are another company that makes oversized bikes with wheels with a 36″ diameter.

    Bicycles that use wheels larger than 29″ are almost always custom-built, since the demand for them is so low.

    For those taller than 6’6″, you may require a larger bike than is sold in most cycling stores. Normally bikes for taller riders will still utilise 29″ wheels, but if you have the budget to cover it, a 32 or 36-inch bespoke made bike could serve you very well. 

    As these 32″ bicycles are almost always custom-built, they are much more expensive than bikes that use standard wheel sizes. You may be able to find a 29er that’s suitable for you. 

    If you want to order a bike with oversized wheels, check out DirtySixer bikes.

    Compared to 29-inch bike wheels, 36-inch wheels would be much more comfortable to ride due to their massive attack angle.

    However, it’s almost impossible to find a manufacturer that would make a 36″ wheel for you and the cornering on a bike with 36″ wheels would be sluggish and heavy.

    Surprisingly, 36″ bike wheels aren’t the largest bike wheels ever made, read about the largest bike ever made below.

    39" Bike Wheels

    39″ bike wheels are, at this stage, only a concept. However Patrick Ng, a 3D artist and visualizer created a 3D render of a mountain bike with 39-inch wheels. 

    Bike wheel size - 39"
    Bicycle wheel size guide - 39 bike wheels

    This concept is unique in the sense that it incorporates chain-steerer handling. Without this workaround, the large 39″ bike wheels would likely clip a rider’s toes when cornering.

    One issue a bike like this would face is the strength of its wheels. Larger wheels are weaker and more prone to damage than small wheels, which is why bikes like BMXs traditionally use small 20″ wheels to withstand heavy impacts.

    Biggest Bike Wheels in the World

    Biggest Bike in the World

    The largest rideable bicycle ever created has a wheel diameter of 3.3m and was created by Didi Senft from Germany in 2012.

    You will not find a bike bigger than this and you can imagine how difficult it would be to get on and off this bike, let alone get it moving!

    Bike Wheel Size FAQs

    Measuring kids’ bike wheels is super straightforward.

    Simply measure the width/diameter of one of the bike wheels from the top of the tire to the opposite side. 

    This guide explains how to measure a bike wheel following the simplest method. 

    If you couldn’t find a measurement on your bike’s tire, you might want to measure the size of your bike wheel. 

    The easiest way to measure your bike wheel size is to measure the diameter of the wheel (from the highest point of the tire to the opposing side) and then measure the width across the top of the tire. 

    For a road bike a common measurement example would be a 700mm diameter and a 25mm tire width. These measurements equate to a 700 x 25c bike wheel size. 

    For instructions on how to measure wheels without a tire or for detailed step-by-step images, you’ll want to read my simple bike wheel measuring guide.

    Some bicycle wheel measurements include tire height, whereas others don’t. 

    The measurement “700c” refers to a wheel & tire with an approximate diameter of 700mm.

    On the other hand, a “622” on a bike wheel is a measurement known as bead seat diameter.

    The bead seat is often found inside the rim of a bike wheel, so the wheel size 622 refers to the rim. 

    The most common size of bike wheel nut (for attaching your wheel to your frame) is normally 15mm wide (0.6″), so you’ll require a 15mm wrench to adjust these nuts. 

    Bike Wheel Size Guide - Conclusion

    Hopefully, this guide has helped to answer a few of your bicycle wheel-related questions

    As we found out in this in-depth guide, there are many different bike wheel sizes, some old, some new, some common and some rare. 

    The most important thing to understand is how to properly measure a bike wheel and how to measure for bike tire size.

    Without understanding these simple steps, you’ll have a hard time replacing inner tubes or old tires if you don’t know your existing sizes.

    In addition, we recommend using a top-quality bike lock to secure your bike. Without one, you’ll be leaving your noble steed vulnerable to theft.

    Recent Updates:

    Author of This Post:
    Picture of James Grear (Lead Editor)
    James Grear (Lead Editor)

    Understanding how devastating it is to have a bike stolen, I've researched & immersed myself in the world of bicycle security since 2013.

    I then built BikeLockWiki in 2019 to share everything I'd learned with the worldwide cycling community so that cyclists can improve their bike security skills and make informed decisions when purchasing new products and services.

    Learn More about Me & BikeLockWiki here.

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