specialized giant cube cannondale merida castelli endura altura
A mountain biker riding a Merida electric hardtail mountain bike through an overgrown trail

Bike Size

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. This is how to measure your height.

Now you know your height measurement have a look at the typical bike size chart below to see what size is best for you. Alternatively, go to the brand specific bike sizing charts for the model that you are interested in. You may also need your leg inseam measurement for some brands bike  size charts.

A graphic showing how to measure your height

Frame Size

XXS - 44cm/13"




XS - 48cm/15"




S - 51cm/16"




M - 54cm/18"




L - 56cm/19"




XL - 58cm/20"




XXL - 60cm/21"




XXXL - 62cm/22"




Typical bike sizing table(Click to expand)


Bike size (cm and Inch)

4’8” – 5’1”  |  143 – 155 cm

44cm/13” – XXS

5’1” – 5’4”  |  155 – 163 cm

48cm/15” – XS

5’4” – 5’7”  |  163 – 170 cm

51cm/16” – S

5’7” – 5’10”  |  170 – 178 cm

54cm/18” – M

5’10” – 6’0”  |  178 – 183 cm

56cm/19” – L

6’0” – 6’3”  |  183 – 191 cm

58cm/20” – XL

6’3” – 6’5”  |  191 – 196 cm

60cm/21” – XXL

6’5” – 6’9”  |  196 – 205 cm

62cm/22” – XXXL

Do sizes vary for different types of bikes?

Road bike sizing and mountain bike sizes are slightly different and the units used in bike sizes vary depending on type and brand. Road bike sizes are usually given in centimetres, while mountain bike frame sizes are quoted in inches. Fortunately, our bike size chart takes away the guesswork as it suggests mountain bike frame size and road bike frame size in either inches or centimetres alongside manufacturers bike size charts.

Many bike manufacturers will quote bike sizes as S, M, L or small, medium or large etc. on some or all their models. Kids bike sizes are usually based on wheel size. Some MTB sizing guides will use inches while you might find road bike sizes  in centimetres.

Mountain bike and road bike sizing

For model specific sizing please check the Sizing Tab on the product page of the bike that you are interested in.

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 346501, chat with Live Help or email info@tredz.co.uk and we will be happy to assist you.

What size frame do I need if I am in-between sizes?

Sometimes the bike sizing chart or bike size calculator will recommend two different bike frame sizing options. This means that both the larger and smaller road bike frame size or mountain bike frame size recommended will be suitable. To help you make this personal choice we asked Dr. Barney Wainwright form the Boardman Performance Centre for some advice.

In our bike sizing video, Dr. Wainwright explains that most bikes aren’t restricted by height, as the saddle is easy to adjust. The key measurement is reach which is how long the bike feels in the riding position. Reach is affected by your trunk length as well as the length of your arms. Trunk length, also known as upper body length or sitting height, is the measurement from your hips to your shoulders.

If your trunk length or sitting height is longer than average, then the larger of the two sizes recommended in the size chart will be ideal.

If on the other hand you have a shorter than average trunk height, then the smaller of the two recommended sizes will probably be best for you.

Once you have your bike there are some adjustments that you can make to fine-tune the fit. Have a look at the other videos in our Boardman Performance Centre bike sizing series in our Bike Fitting Guide to see how easy it is to get the right bike fit.

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

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

Women tend to have shorter upper bodies than men, so the women’s specific frames are shaped differently. The top tubes are slightly shorter than unisex bikes which reduces reach, so female cyclists won’t feel so stretched out. As this doesn’t affect the seat tube length (saddle height) or stand-over clearance, our bike size calculator is suitable for all types of bikes.

Women who are between sizes on a Unisex bike may choose the smaller of the two recommended sizes. See the what if I am between sizes section for more on this.

Woman cycling on a Liv road bike

Brand specific size guides

This is where you will find your Specialized Size guide as well as road, hybrid and MTB sizing charts from brands like Liv, Giant, Merida, Orbea and Scott. Use these bike size guides instead of a bike sizing calculator to find what frame size you need for bikes from these cycling brands.

Bike Geometry

Discover what the numbers mean

MTB Geometry Guide

MTB Geometry Explained

Mountain bike geometry can be confusing. Here we explain the most important MTB geometry numbers, what they are and what they mean. 

Road Bike Geometry

Road Bike Geometry Explained

Here we explain the most important geometry numbers, what they are and what they mean.

Most Popular Bikes