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Bike Sizing Guide

Bike Size Guide

What size bike do I need?

Choosing the right frame size for your new bike makes all the difference, because if the fit is good you will be more comfortable when cycling, the handling will be easier and you will be able to ride more efficiently. In this bike size guide we will explain how you can use the bike size charts and sizing calculator to get the ideal fit.

To choose the right size bike you will need to match your height and inside leg measurement to the frame size recommended by the manufacturer. To make this easier you can use our handy bike size calculator.

Do sizes vary for different types of bikes?

Road bikes and mountain bikes are sized slightly differently and the units used vary depending on usage and brand. Road bike sizing is usually given in centimetres, while mountain bike sizes are often quoted in inches.  Sometimes, manufacturers will quote sizes as small, medium or large etc. on some or all their models.  Fortunately, our bike size calculator takes away the guesswork as it suggests sizes in either inches or centimetres as well as S, M or L sizing . Children's bike sizes are usually based on wheel size.

MTB vs Road bike sizing

How do I choose the right size bike?

Choosing the correct size bike is easy. All you need to do is measure your height and your inside leg (inseam) and then enter those measurements into our bike size calculator.

Measure your height

Simply stand on a flat surface, upright against a wall with your legs together and shoulders back. Make sure you take your shoes off. Place a pencil on top of your head and holding it parallel to the floor make a little mark on the wall.

Measure your height for bike fit

Measure your inside leg

Stand with your back against a wall (no shoes). Place a book or ruler between your legs at your crotch. Get a friend to measure from the floor to the top of the book/ruler, making sure it is level.

Measure your inside leg for bike fit

Typical Bike Sizing Chart


Inside leg

Road bike size

Mountain bike size

152cm / 5'.0"

71cm / 28"

48cm (XX Small)

15" (X Small)

160cm / 5'.3"

75cm / 29.5"

51cm (Small)

16" (Small)

170cm / 5'.7"

79cm / 31"

54cm (Medium)

17" (Medium)

175cm / 5'.9"

83cm / 32.5"

56cm (Large)

18" (Medium)

180cm / 5'.11"

85cm / 33.5"

57cm (X Large)

19" (Large)

188cm / 6'.2"

89cm / 35"

60cm (XX Large)

20" (Large)

196cm / 6'.5"

93cm / 36.5"

63cm (XXX Large)

21" (X Large)

Can I use the bike size calculator for women’s specific bikes?

Yes, typically women’s specific bikes have different frames to unisex bikes but they are sized in the same way. Women tend to have shorter upper bodies than men so the frames are shaped differently.

Women's bikes tend to have shorter top tubes compared to a similarly sized unisex bike. This makes the bike slightly shorter than a unisex bike so female cyclist will feel less stretched out on women’s bike.

As this doesn’t affect the seat tube length (saddle height) or stand-over clearance, our bike size calculator is equally suited to both unisex and women’s specific bikes.

Women specific bike sizing

What size bike should I choose if I am between sizes?

Sometimes our bike sizing calculator will recommend two different sizing options. This means that both the larger and smaller sizes recommended will be suitable.It is a personal choice but, if you are unsure, there are a couple of rules of thumb:

Road bikes - choose the smaller size. This is because it is easier to make a small road bike bike bigger (by raising the saddle or fitting a longer stem) than it is to make a big road bike smaller.

Mountain bikes - choose the larger size. You don't want to feel too cramped on an MTB and lengthening the stem on a smaller bike can adversely affect the handling. You will better off with a slightly larger bike and shortening the stem if necessary, as this often improves handling.

What bike to choose when between sizes

Bike Size Calculator

Your mountain bike size is:

Frame (inches):16/17
Frame (size):Small / Medium

Your road bike size is:

Frame (cm)
Frame (size)

*For model specific sizing please check the product page.

**Please note all sizing information is to be used as a guide only. This is because bike sizes can vary for different brands and models. If you are unsure which size bike will be best for you, our bike specialist team are here to help. Call us on 01792 3465601, chat with Live Help or email info@tredz.co.uk and we will be happy to assist you.