A mountain biker riding a Merida electric hardtail mountain bike through an overgrown trail A mountain biker riding a Merida electric hardtail mountain bike through an overgrown trail

Bike Size

What size bike do I need?

Below you'll find our general bike frame size guide, however it's always best to check the bike sizing chart on the specific model which will be more accurate once you've narrowed down your options. Click on the frame size you want to see the bike models that are right for you.

Bike Size
Road Bike Size
Mountain Bike Size *
4’8” – 5’1”
143 – 155 cm
13” (33 cm)
5’1” – 5’4”
155 – 163 cm
15” (38 cm)
5’4” – 5’7”
163 – 170 cm
16” (41 cm)
5’7” – 5’10”
170 – 178 cm
18” (46cm)
5’10” – 6’0”
178 – 183 cm
19” (48cm)
6’0” – 6’3”
183 – 191 cm
20” (51 cm)
6’3” – 6’5”
191 – 196 cm
21” (53 cm)
6’5” – 6’9”
196 – 205 cm
22” (56 cm)

* Note: Mountain bikes are sized differently to road bikes. Typically, they are sized in inches as the first MTBs were produced in the USA. European brands like Lapierre and Haibike like to use centimetres for all their bikes. The measurements of their mountain bikes doesn’t match their road bikes but are like a simple conversion from the inches measurement instead. This is why we have included cm measurements in brackets for the mountain bike column.

For more accurate information on sizing a bike please check the specific bike frame size chart for the model you're are interested in. You will find the model specific size chart information on the product page of the bike in question. Alternatively, go to the brand specific bike sizing charts for the model that you are interested in.

Alternatively contact us via Live Chat. Available until 10pm, 7 days a week

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

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

Sometimes bike sizing charts or our 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 for you. To help you make the right choice we asked a bike specialist Dr. Barney Wainwright for some advice.

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.

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.

Brand specific size guides

The above information is a general overview to bike sizing, model specific sizing can be found on all the product pages for the most popular brands, if in doubt use these tables for the most specific sizing information.

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 metrics 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.

Frequently Asked Questions

What size bike should I buy for my height?

To find the right size bike for your height look at this bike size chart first. This will give you a general idea of the best size for you but be sure to check the individual size chart for the model of bike you want before you buy.

How do you determine the size of your bike?

The size of your existing bike will be shown somewhere on the frame, usually a sticker on the seat tube or top tube. Traditionally bike sizes are determined by the length of the seat tube, but most modern bikes are sized differently.

What size bike should I buy for my child?

Our kids bike size chart shows bike sizes for children. Kids bikes have different wheel sizes and the best one for your child will depend on their age and their height.

Should your feet touch the ground on a bike?

When you are learning to ride it is helpful if both your feet can touch the ground when you sit on a bike. However, once you are confident you should raise the saddle to position that makes pedalling easier. Find out how to set your saddle height correctly.

Should your legs be straight when riding a bike?

Your legs should never be completely straight when pedalling. See our guide to find out how to set your saddle height correctly so that your leg has the right amount of bend when you ride.

Can a bike be too big?

Yes, a bike can be too big. If a bike is too big it will be difficult to ride as well as being uncomfortable. Buying a bike that is too big for a child so that they will grow into it eventually could put them off cycling.

What age is a 26 inch bike for?

26 inch wheel mountain and hybrid bikes are ideal for 11 to 14 year old kids. Shorter adults may also find that a 26 inch wheel bike offers the best fit.

What does a 26 inch bike mean?

26 inch bikes are bikes with 26 inch wheels. These are usually small size mountain bikes suitable for junior riders.

Can adults ride 24 inch bikes?

Most 24 inch wheel bikes are too small for adults to ride as they are designed for kids about 10 years old. The exception to this is 24 inch wheel cruiser BMX bikes which are suitable for adults.

What height is a 24 inch bike for?

A 24 inch wheel bike is suitable for junior riders between 135cm and 145cm tall. Cruiser BMX bikes with 24 inch wheels are suitable for adults who like this riding style.

What size is a 21 inch bike frame?

A 21 inch bike frame is an XXL size suitable for people over 6 foot 2 inches tall. See our bike size chart for more bike sizes.

Where should I sit on my bike saddle?

Your ‘sit bones’ should be properly supported when you sit on your bike saddle. The ideal position will depend on the style of bike. See our bike fitting guide for more.

Does frame size matter on a bike?

The frame size is crucial to your fit on a bike. If your bike’s frame is too big or small then the bike will be uncomfortable and difficult to ride. See our bike size chart to find the right size bike for you.

What is a good size bike for a 5 foot woman?

An extra small or XS size bike is ideal for a 5’ tall woman. An XS size bike is equivalent to a 48cm road bike and a 15 inch mountain or hybrid bike. See our bike size chart for more.