SIZING GUIDES AND BIKE SIZE CALCULATOR

Bike Size Guides and FAQs

Click on the options below to get more information about the type of bike you're interested in.

Bike Sizing FAQ's

When buying a new bike, sizing is vital. Getting a bike that doesn't fit won't only mean you'll be uncomfortable but you're instantly on the road to disliking cycling - And that's a bad thing. Even if you know your size, have a read through our handy guide before buying a bike to check your new ride is going to be your perfect match.

HOW ARE BIKES SIZED?

All adult bikes are measured by their frame size. This is typically the length of the seat tube: the near-vertical tube that the saddle and seat post slide into. Manufacturers will measure these slightly differently. However, the rule of thumb is to measure from the centre of the bolt which fastens the crank arms, all the way up the frame, to the top of the seat tube. Some brands (especially American) stop short of the top, only measuring to the point where the top tube meets the seat tube.

WHAT TYPE OF BIKE DO I NEED?

It's important to decide what sort of bike you need. There are three main categories of bike: road, mountain and commuter. Please note that there are many sub categories such as sportive road bikes and 29er mountain bikes, but generally the sizing will be the same.

DO SIZES VARY FOR DIFFERENT TYPES OF BIKE?

It's worth noting that road and mountain bikes are subject to different sizing. Firstly, road bikes usually come in metric, centimetre measurements, whereas mountain bikes are generally measured in inches. Just to add to the confusion, some manufacturers do away with the measurements and rely on a small, medium and large size guide.

WHAT DO I MEASURE?

In order to size a bike correctly you should consider your height and inside leg measurement along with your riding style and the style of the bike itself. Measuring your height is best done by standing upright against a wall with your legs together (shoes off) and shoulders back. Place a pencil on top of your head, holding it parallel to the floor and mark the wall. You can now measure your height easily against the wall. Your inside leg measurement is taken from the floor (again, no shoes) to your crotch.

IT'S ABOUT CLEARANCE NOT CONTACT!

The distance between you, specifically your crotch and your bike's top tube (aka crossbar), is known as clearance. Clearance is indicated by standing over the bike, forward of the saddle and measuring the distance from your crotch to the top tube. It is important to be able to stand safely over the bike when stationary. Therefore, a clearance of at least two inches should exist on all the bikes you ride. It can be thought of as a safety net to prevent injuring yourself if you need to jump forward off the saddle suddenly.

WHAT ARE ROAD BIKES?

This is what you see in the Tour de France and other cycle races. Thin, fast rolling tyres are fitted to stiff frames which also feature 'drop' handlebars. Although you can use a road bike on cycle paths, you might find it a bit uncomfortable. Accurate road bike fitting is crucial as getting it wrong can lead to a very awkward ride.

WHAT ARE COMMUTER / HYBRID BIKES?

Mid-point between a road and mountain bike. Hybrids will have the frame of a mountain bike, but often the wheels of a road bike to allow them to roll faster and smoother. You will sacrifice some comfort from the thinner tyres, but the mountain bike frame, bars and position will be more comfortable than a road bike.

WHAT ARE MOUNTAIN BIKES?

These are designed for off road use, so they will generally have fatter tyres to absorb the rough terrain and usually be fitted with at least a front suspension fork. The downside of fatter tyres is increased rolling resistance, so a mountain bike won't get you where you are going as fast on the road as a hybrid.

Mountain Bike Size Guide

Your Height Suggested Bike Size
Feet and Inches Centimetres Frame Size (Inches) Frame Size
4' 10" - 5' 2" 148cm - 158cm 13" - 14" X-Small
5' 2" - 5 '6" 158cm - 168cm 15" - 16" Small
5' '6" - 5' 10" 168cm - 178cm 17" - 18" Medium
5' 10" - 6' 1" 178cm - 185cm 19" - 20" Large
6' 1" - 6' 4" 185cm - 193cm 21" - 22" X-Large
6 '4" - 6' 6" 193cm - 198cm 23" - 24" XX-Large

To determine your ideal mountain bike size all you need to know are your height and inside leg measurement. We have prepared an easy to follow guide to ensure that you choose the right size mountain bike.

HOW ARE MOUNTAIN BIKES (MTB) MEASURED?

Mountain bikes are measured by the distance between the centre of the bottom bracket and the top of the seat tube. Generally the unit is in inches and adult sizes usually range from 14" – 24". The length of the top tube will vary depending on the seat tube length, and will get longer as the frame size gets bigger to accommodate a taller rider. For gravity bikes such as downhill bikes, dirt jump bikes, BMXs and 4x bikes, sizing is not as critical as bikes are designed to be smaller in proportion to the rider, therefore they are usually described as short, medium or long.

KEY MEASUREMENTS - HEIGHT

Manufacturer's recommendations are based on your height, so if you are 5"10, you are going to be best suited to riding an 18" bike. This is however based on the assumption that your inside leg is 31"-33". If you are outside of that range (and it's not unusual if you are) you might have to adjust the size of the bike accordingly. It is easy to find your height with a tape measure and a helper – it can be done on your own but an assistant makes it easier. Without shoes, stand against a wall wearing and place a book on your head, then simply measure the distance from the bottom of the book to the floor.

WHAT IS STANDOVER?

Standover is the length of your inside leg minus the top tube height, i.e. the difference between 'you' and the top tube of the bike. The standover height of a bike can usually be found in the geometry section on our product pages or on the manufacturer's website – if you can't find it, please call us and we'll be able to give you an answer. You should allow at least 1-2" of clearance between you and the bike so if you dismount quickly you don't land on the top tube – for full suspension bikes this figure should be slightly more.

TIPS

Female specific bikes don't just come in different colour schemes with flowers and patterns – women generally have longer legs and shorter bodies than men, so female specific bikes have a shorter top tube to suit the female form better. If you find you have bought a bike and it's slightly the wrong size, or if you feel you are in between sizes, there are still things you can do to fix it. Moving the saddle on its rails can help, as does a longer/shorter stem and handlebar position. It's possible to get a bike to fit you perfectly, whatever shape you are, so don't lose hope just yet.

Sizes do vary between manufacturers so just because your old bike is one size, doesn't automatically mean your new one will be too. Mountain bike sizes are completely different to road bike sizes, so please don't cross reference the two.

Road Bike Size Guide

Your Height Suggested Bike Size
Feet and Inches Centimetres Frame Size (cm) Frame Size
4' 10" - 5' 0" 148cm - 152cm 47cm - 48cm XX-Small
5' 0" - 5 '3" 152cm - 160cm 49cm - 50cm X-Small
5' '3" - 5' 6" 160cm - 168cm 51cm - 53cm Small
5' 6" - 5' 9" 168cm - 175cm 54cm - 55cm Medium
5' 9" - 6' 0" 175cm - 183cm 56cm - 58cm Large
6 '0" - 6' 3" 183cm - 191cm 58cm - 60cm X-Large
6 '3" - 6' 6" 191cm - 198cm 61cm - 63cm XX-Large

After spending hours researching and dreaming of your new bike, the tricky and often misunderstood task of choosing the correct bike size can sometimes be overlooked. If you buy the wrong parts you can simply swap them, but buying an incorrect bike will mean a lot of discomfort and even pain for the rider.

HOW ARE ROAD BIKES MEASURED?

Road bikes are generally measured in centimetres with adult sizes usually ranging from around 48cm – 62cm. The length is the distance between the centre of the bottom bracket and the top of the seat tube. The length of the top tube will vary depending on the seat tube length and will get longer as the frame size gets bigger to accommodate a taller rider.

KEY MEASUREMENTS

Most manufacturers build a bike based on rider height. So if you are 5"10, you are going to be best suited to riding a 56cm bike. However this does assume your inside leg is 31"-33". If you are outside of that range (and it's not unusual if you are) you might have to adjust the size of the bike accordingly. It's easy to find you height with a tape measure and a helper – it can be done on your own but an assistant makes it easier. Without shoes, stand against a wall and place a book on your head, then simply measure the distance from the bottom of the book to the floor.

WHAT IS STANDOVER?

Stand over is effectively the height of your inside leg minus the top tube height – the difference between 'you' and the top tube of the bike. The stand over height of a bike can usually be found in the geometry section on our product pages or the manufacturer's website – if you can't find it, please call us and we'll be able to find it for you. You should allow at least 1-2" of clearance between you and the bike so you don't land on the top tube if you have to dismount.

TIPS

Female specific bikes don't just come in different colour schemes with flowers and patterns – women are generally made with longer legs and shorter bodies than men, so female specific bikes will have a shorter top tube to adjust the bike accordingly. If you find you have bought a bike and it's slightly the wrong size, or if you feel you are in between sizes, there are still things you can do to fix it. Moving the saddle on its rails can help, as can a longer/shorter stem and handle bar position. It's possible to get a bike to fit you perfectly, whatever shape you are, so don't lose hope just yet.

Sizes do vary between manufacturers so just because your old bike is one size, doesn't automatically mean your new one will be too. Mountain bike sizes are completely different to road bike sizes, so please don't cross reference the two.

TT/Triathlon Bike Size Guide

Your Height Suggested Bike Size
Feet and Inches Centimetres Frame Size (cm) Frame Size
4' 10" - 5' 0" 148cm - 152cm 47cm - 48cm XX-Small
5' 0" - 5 '3" 152cm - 160cm 49cm - 50cm X-Small
5' '3" - 5' 6" 160cm - 168cm 51cm - 53cm Small
5' 6" - 5' 9" 168cm - 175cm 54cm - 55cm Medium
5' 9" - 6' 0" 175cm - 183cm 56cm - 58cm Large
6 '0" - 6' 3" 183cm - 191cm 58cm - 60cm X-Large
6 '3" - 6' 6" 191cm - 198cm 61cm - 63cm XX-Large

As one of the fastest growing sports in the world, triathlon pushes levels of fitness and stamina to the absolute limit. A properly fitting triathlon bike will provide the ultimate partnership for the section of the race covering the longest distance.

TRIATHLON PERFORMANCE

Triathlon bikes are unique in geometry in order to achieve the best performance and aerodynamics, although riders themselves will always create the majority of aerodynamic drag. It is worth mentioning that triathletes are not bound by International Cycling Union rules, so many triathlon bikes are UCI illegal. Some triathlon participants use modified road bikes with clip on aerobars which is a cheaper alternative for tackling undulating bike courses, but investing in a purpose-made triathlon bike will help achieve a better performance, especially for racing on flat and straight terrain.

BMX Bike Size Guide

Rider Height Suggested BMX Size
Feet and Inches Centimetres Approximate Age Wheel Size
3' 7" - 4' 0" 110cm - 122cm 5 - 7 Years 16"
4' 0" - 4' 10" 122cm - 147cm 7 - 11 Years 18"
4' 10" - 6' 4" 147cm - 193cm 11+ Years 20

BMX (bicycle moto-cross) arose as a sport in the early 1970s as a result of kids wanting to emulate their moto-cross heroes but with pedal power. It rapidly grew into a worldwide phenomenon reaching its peak in the mid eighties. As with most phenomena its popularity waned and it all but disappeared from the mainstream media; but it didn't die, far from it. The sport went very much underground and split into 3 distinct disciplines. In recent years it has exploded again, race BMX has become an Olympic sport and no 'extreme' TV channel would be complete without a BMX competition.

WHAT SIZE FREESTYLE BMX DO I NEED?

Freestyle BMXs (the common type you rode as a kid) are generally all one size. The toptube (bit between the seat and the bars) can vary by an inch or two, but the difference in size can be countered by moving the bars. As a guidline, BMX bikes will suit a rider nine years or older. A tall eight year old might be able to ride one, but due to the added weight (BMX bikes are built to be solid), a younger rider might struggle.

GENERAL BMX GUIDE

If you really want to be sure, the height of the saddle will be a MINIMUM of 23inches off the ground. If your child's inside leg is shorter than this, they will be too short to safely place their feet on the ground and would be best waiting until the next growth spurt. There are smaller 18inch wheel BMXs available, but they will still have a 21-22inch saddle height and are still heavier so will still suit riders from the age of around eight years. There is no upper limit for riders – a 6 foot tall, pro BMXer will use the same size bike – the smaller size allows greater freedom of movement so bigger bikes aren't required.

WHAT BMX EQUIPMENT DO I NEED?

It's always important to get the right safety gear. For racing you will need a full-face helmet whereas for the freestyle and jumping you will want to use a lighter helmet to just cover the top of the head, these are known as skate style helmets. For all disciplines it is recommended you wear a long sleeved shirt, long trousers or jeans and gloves. Rubber soled skate style shoes are ideal as they have flat soles, which are good for grip. Extra pieces of body protection kit such as elbow pads, kneepads and shoulder pads are not essential although they are always a good idea especially if you are new to the sport.

Womens Bike Size Guide


Women's Road Bike Size Guide

Rider Height Suggested Frame Size
Feet and Inches Centimetres Frame Size (cm) Frame Size
4' 10" - 5' 1" 147cm - 155cm 44cm - 46cm XX-Small
5' 1" - 5' 3" 155cm - 160cm 47cm - 49cm X-Small
5' 3" - 5' 5" 160cm - 165cm 50cm - 52cm Small
5' 5" - 5' 8" 165cm - 172cm 53cm - 55cm Medium
5' 8" - 5' 10" 172cm - 180cm 56cm - 57cm Large

Women's Mountain / Hybrid Bike Size Guide

Rider Height Suggested Frame Size
Feet and Inches Centimetres Frame Size (Inches) Frame Size
4' 10" - 5' 2" 148cm - 158cm 13" - 14" X-Small
5' 2" - 5' 6" 158cm - 168cm 15" - 16" Small
5' 6" - 5' 10" 168cm - 178cm 17" - 18" Medium
5' 10" - 6' 1" 178cm - 185cm 19+" Large

Cycling has long been a man's world where women have had to adapt themselves to riding men's bikes and only being able to adjust the saddle height. While this suits some women, it's not ideal for the majority who find they suffer neck, shoulder or back strain as a result. Most manufacturers now produce women-specific models in addition to the standard models, often using D4W (Designed for Women), WSD (Women Specific Design) or (L) in the name. All categories therefore tend to offer a choice of women's bikes. You can easily find these by using the Gender filter for 'Women's Specific' bikes.

WHAT ARE THE DIFFERENCES COMPARED TO MENS BIKES?

Women's upper bodies and arms are generally shorter than mens while their legs tend to be longer. Basically if a woman sits on a man's bike and could just reach the floor with their feet, they would have to stretch too far forward to reach the handlebars. The 'women specific' bikes therefore have a shorter reach and a slightly raised handlebar position to help take the strain away from the arms, shoulders and neck. Being sat more upright places more weight on the seat so a women specific saddle is been designed to accommodate the different shaped pelvis and wider sit bones.

WHAT OTHER FEATURES SHOULD I LOOK OUT FOR?

Women specfic bikes feature thinner handgrips (smaller in diameter), Narrower bar width and shorter reach brake levers. To compliment the bikes, there is also a wide range of women's specific clothing available.

Children's Bike Size Guide

Rider Height Suggested BMX Size
Feet and Inches Centimetres Approximate Age Wheel Size
3' 0" - 3' 6" 91cm - 107cm 2 - 4 Years 12"
3' 7" - 4' 0" 110cm - 122cm 5 - 7 Years 16"
4' 0" - 4' 10" 122cm - 147cm 7 - 11 Years 18"
4' 10" - 6' 4" 147cm - 193cm 11+ Years 20"

A kid's bike is designed to take account of their smaller physical dimensions. While the most common sizes for children's bikes are 12, 16, 20 and 24-inch wheel bikes, some companies also make 14-inch and 18-inch wheel sizes to bridge the gap between sizes. These two sizes are less common and parts or spares such as tyres and tubes may be harder to find. Most good bikes of each wheel size will be adjustable by raising the saddle and handlebars as the child grows.

WHAT BIKE SIZE DO I NEED FOR A 2-4 YEAR OLD?

Around the age of two children should be able to ride a 12-inch wheel bike. These bikes typically come with training wheels (stabilisers) and 'direct drives', allowing the child to stop and go forward or backwards using the pedals, as brake levers would be too much for tiny hands.

WHAT BIKE SIZE DO I NEED FOR A 5-7 YEAR OLD?

At about four years of age, most kids will fit on a 16-inch wheel bike. Again most of these come with stabilisers and almost all have 'real' tyres with inner tubes. Most will have a coaster brake which works when the child pedals backwards although some are fitted with hand operated brake levers on the handlebars.

WHAT BIKE SIZE DO I NEED FOR A 7-9 YEAR OLD?

By the time the child reaches about seven they should have already mastered the basics of balance and stopping. The 20-inch wheel bike introduces gears on some models, there may also be features that you would see on an adult bike like front and rear suspension and even disc brakes.

WHAT BIKE SIZE DO I NEED FOR A 9-12 YEAR OLD?

Around nine years of age, the majority of children will be stepping up to 24-inch wheel bikes, known as 'junior bikes'. As the wheel size gets bigger the bike becomes longer. This is one of the biggest leaps in bikes as it is a smaller version of nearly all adult mountain bikes. Almost all 24-inch bikes come with gears, suspension and the other components of a full size cycle.

WHAT BIKE SIZE DO I NEED FOR A 13 YEAR OLD PLUS?

Once a child reaches their early teens, they'll move to small adult cycles with 13-14 inch frame sizes. The type of bike (e.g. road bike, mountain bike, BMX etc) then depends on the child's riding preferences. Our relevant bike guides have more information. Please see our kids bike sizing table as a guide to help you choose the right size bike for your child. If you feel you'd like further help please contact us and we will do our best to help you make your choice.

Cycle Clothing, Equipment and Brands Size Guides

Click on the options below to get more information about the type of product you're interested in.

General Cycle Clothing Size Guide

Mens Clothing Size Guide
Size X-Small Small Medium Large X-Large XX-Large
Continental 1 2 3 4 5 6
Italian / Far Eastern S M L XL XXL XXXL
Chest (in inches) 30-33 33-35 36-38 39-41 42-44 44-46
Waist (in inches) 24-26 27-29 30-32 33-35 36-39 40-42
Womens Clothing Size Guide
Size X-Small Small Medium Large X-Large XX-Large
Ladies Size 6-8 8-10 10-12 12-14 14-16 18+
Continental 1 2 3 4 5 6
Italian / Far Eastern XXS XS S M L XL
Chest (in inches) 30 32 34 36 38 40
Hips (in inches) 34 36 38 40 42 44
Sports Bra 0 32A/B/C & 34A/B 34B/C & 36B/C 36C/D & 38C/D 36D/DD & 38D/DD 0

Cycling Jackets Size Guide

Cycling Jackets Size Chart
Size X-Small Small Medium Large X-Large XX-Large
Chest (in inches) 30-33 33-35 36-38 39-41 42-44 44-46

Cycling Legwear Size Guide

Cycling Legwear Size Chart
Size X-Small Small Medium Large X-Large XX-Large
Waist (in inches) 24-26 27-29 30-32 33-35 36-39 40-42

Cycling Shoes Size Guide

Cycling Shoes Conversion Guide
Euro 36 UK 37 38 39 40 41 42 43 44 45 46
UK 3.5 4 5 6 6.5 7 8 9 10 10.5 11 12

Cycling Gloves Size Guide

Rider Height
Size Measurement Inches
X-Small 7 2 1/8- 2 5/8
Small 8 2 5/8 - 3 1/8
Medium 9 3 1/8 - 3 5/8
Large 10 3 5/8 - 4 1/8
X-Large 11 4 1/8 - 4 5/8
XX-Large 12 4 5/8 - 5 1/8
* Please note: Castelli gloves do not conform to the above Guide, they are generally a size smaller.

** Please note that all sizing information is provided as a guide and the products can vary for different models/type of product. For the most accurate sizing information, you can either call us on 01792 799508, email us via our online contact form or chat with us on Live Help and we'll be happy to help. Any bike ordered at the incorrect size will be subject to a £35 collection fee.

Tredz Online Sales, Castell Close, Swansea Retail Park, Llansamlet, Swansea, SA7 9FH
E-mail: sales@tredz.co.uk | Tel: 01792 799508