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Bike Size Guide

Ensuring your bike is the right size for you is probably the most important part of buying a new bike. It's important that you pick the right size for safe and comfortable riding.

Choosing the Right Size for Children

Three children and an adult woman are cycling on a path

Children's bikes are generally organised by the wheel size of the bike, with the wheel size recommended for an age range based on the average size of a child within that range. There's no hard and fast rule as to what size bike fits what age of child, but if your child is above or below the average height, consider moving up or down a bike size.

It is important to consider your child's confidence in cycling. A too large bike may prove daunting, or require the additional purchase of stabilisers.

Wheel SizeAge Range
12" Wheels2½ to 4
14" Wheels3 to 5
16" Wheels5 to 7
18" Wheels6 to 7
20" Wheels6 to 8
24" Wheels9 to 11

Choosing the Right BMX Bike

BMX bikes are available with 16", 18", 20" and 24" wheels, but primarily come with 20" wheels. Therefore, they can be used by anyone from around 7 years of age and older, and the benefits of buying a single bike that will last a child into adulthood is one of the selling points for BMX bikes.

Because a BMX bike is often more of a style choice, you'll find that you'll be looking more for a particular brand or model rather than a particular size.

Choosing the Right Size for Adults

Adult bikes are organised by the frame size, with the wheels being 26", 29" or 700c, depending on the type of bike you're purchasing. The frame size is measured from the top of the frame at the point where the seat post is inserted, down to the centre of the axle carrying the pedal arms.

Outline of a bicycle with the space between the seat post and the axle shown via a red double-headed arrow

For heritage, city and mountain bikes, this frame size is usually represented in inches, and for hybrid, touring and road bikes, this is usually represented in centimetres.

To choose the ideal bike size for you, measure your inside leg from the crotch of your trousers down to the floor, making sure your feet are flat on the ground.

Imperial Frame Sizes

Frame SizeInside Leg Range in InchesInside Leg Range in Centimetres
14"24"-29"61cm-74cm
15"25"-30"63cm-76cm
16"26"-31"66cm-79cm
17"27"-32"69cm-81cm
18"28"-33"71cm-84
19"29"-34"74cm-86cm
20"30"-35"76cm-89cm
21"31"-36"79cm-91cm
22"32"-37"81cm-94cm
23"33"-38"84cm-97cm
24"34"-39"86cm-99cm

Metric Frame Sizes

Frame SizeInside Leg Range in InchesInside Leg Range in Centimetres
35cm24"-29"61cm-74cm
38cm25"-30"63cm-76cm
41cm26"-31"66cm-79cm
43cm27"-32"69cm-81cm
46cm28"-33"71cm-84
49cm29"-34"74cm-86cm
52cm30"-35"76cm-89cm
53cm31"-36"79cm-91cm
56cm32"-37"81cm-94cm
58cm33"-38"84cm-97cm
61cm34"-39"86cm-99cm

The following rules of thumb should be applied when you try a bike for its size:

Road and Racing Bikes: When standing flat-footed on the ground, there should be a minimum of 1" clearance between yourself and the top tube of the frame.

Mountain and Heritage Bikes: When standing flat-footed on the ground, there should be a minimum of 3" clearance betwen yourself and the top tube of the frame.

Any Further Questions?

If you're still not certain about what frame size would be the best, call us on 0845 375 1774 and discuss it with our cycling experts.


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