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road cyclists on Specialized S-Works

Road Bike Size Guide

Choose the right size road bike with our bike size guide. The right size road bike will be more comfortable and more efficient so you can ride quicker.

What size road bike do I need?

Choosing the right road bike makes a real difference. This is because a good fit will mean that you will be more comfortable as you cycle, the handling will be easier and you will be able to ride more efficiently. In this guide, we will explain road bike sizing and how you can use the size charts and bike sizing calculator to get the perfect road bike fit.

Choosing the right size bike is easy. All you need to do is measure your height and inside leg, then use our handy bike size calculator to find out which size bike will fit you best.

Road cyclists on a Cube road bike in Cube clothing

How are road bikes sized?

Road bikes are usually sized either in centimetres or with a general size like medium or large. It is the frame size that determines road bike sizing. 

Classically, frame sizes are based on the length of the seat tube, measured from the centre of the front chain ring to the top of the seat tube. Compact road bike frames, with a sloping top tube, will either show a measurement based on a classic frame or a general size like small or medium. 

Sizes will vary slightly between manufacturers.

Road bikes are measured using seat tube length

How do I choose the right size bike?

All you need to do to choose the right size road bike is to measure your height and your inside leg (inseam) and then use our handy bike size calculator.

Measure your height

Take your shoes off and stand on a flat surface next to a wall with your legs together and shoulders back.

Place a pencil on your head holding it horizontally, make a little mark on the wall and measure the distance from there to the floor.

Measure your height for bike size

Measure your inside leg

With your shoes off, stand with your back against the wall. Place a book or ruler between your legs at your crotch and make sure it is level.

Get a friend to measure from the top of the book/ruler to the floor.

Measure your inside leg for bike size

Road Bike Sizing Chart


Inside Leg

Road bike size

152cm / 5’.0"

71cm / 28”

48cm (XX Small)

160cm / 5’3”

75cm / 29.5"

51cm (Small)

170cm / 5’7”

80cm / 31.5"

54cm (Medium)

175cm / 5’9”

83cm / 32.5"

56cm (Large)

180cm / 5’11”

85cm / 33.5"

57cm (X Large)

188cm / 6’2”

89cm / 35"

60cm (XX Large)

196cm / 6’5”

93cm / 36.5"

63cm (XXX Large)

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

Yes, typically women’s specific road bikes have a different frame geometry to unisex bikes but they are sized in the same way.

Women tend to have shorter upper bodies to men so women’s specific road bikes tend to have a shorter top tube than unisex bikes. As this doesn’t affect the seat tube length our bike size calculator is suitable for both unisex and women’s specific bikes.

Female cyclist on a Liv womens specific bike

Which road bike should I choose if I am between sizes?

Our bike sizing calculator will sometimes recommend two different sizing options. This means that both the larger and smaller sizes recommended will be suitable for you. The one you choose comes down to personal preference but, if you are unsure, the general rule of thumb is to go for the smaller size option.

This is because it is easier to make a small bike bigger (by raising the saddle height and/or fitting a longer stem) than it is to make a large bike smaller.

Male and female road cyclist on gravel road

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.

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