Bike Sizing Guide

Buying a bike that is the right size is possibly the most important part of choosing your new cycle - but which is the right size for you?  A bike too large will be hard work to ride, and a bike too small will be awkward to ride - so use our guide to make sure that your new bike is the correct fit, so that it will be a pleasure to ride.


Sizing Children's Bikes

Children's bikes are probably the hardest to choose the correct size, as all children grow at different rates - and you don't want them to outgrow their new bike in a matter of months. It is important though to avoid the temptation of buying a bike that is too big for them to handle in the hope that they will "grow into it" - a bike too large will be difficult to handle and can be dangerous.  The child MUST be able to manage all the controls safely - that meand not only reaching the handlebars but also that their fingers can reach the brake levers and gears if fitted.  As a general rule, if the child can operate the controls without stretching and touch the floor with the ball of their foot, then they can handle the bike.  The sizing guide below is a suggested guide based on average age/height.


Children's Sizing Suggestions


12" Wheel Cycles - Suitable for ages 2½ to 4.
14" Wheel Cycles - Suitable for ages 3 to 5.
16" Wheel Cycles - Suitable for ages 5 to 7.
20" Wheel Cycles - Suitable for ages 7 to 9.
24" Wheel Cycles - Suitable for ages 9 to 11.
26" (and larger) Wheel Cycles - Adult bikes suitable for ages 11+ (Usually available in a choice of frame sizes - see our guide for Adult's sizing below).



Sizing Adult Bikes


Cycle SizingAdult cycles usually come with wheel sizes of either 26" (Most mountain bikes and some commuter/hybrid bikes), 700c (Road 'racing' bikes, most touring and trekking bikes) and 29" (Some newer mountain bikes, generally referred to as "29'ers"). Folding bikes generally come with a 20" wheel but are designed for larger riders than 20" children's bikes.


The wheel size is usually determined by the style of bike - for correct sizing the frame size on an adult cycle is more important than the wheel size.  Your preferred style of riding can also influence the frame size you choose. Old-fashioned "roadster" bicycles were often designed to be ridden with the seat as low as it can go and the handlebars high in the "sit up and beg" position - and people often chose the largest frame they could comfortably handle.  This is not the case with modern bicycle design - on a correctly sized bike the saddle should be raised and some of the seatpost visible.


The frame size is based on the length of the seat tube (the "near-upright" part of the frame that the saddle's seatpost goes into) - see below for a table of suggested sizing.  For mountain bikes and most leisure bikes this is measured in inches, road/racing bikes are usually measured in centimetres.

When you straddle the bike frame with both feet flat on the ground (stood in front of the saddle) you should be able to clear the top tube (sometimes called the crossbar).  The saddle should be set at a height that, when the pedal is at the bottom of it's stroke, your knee is slightly bent (not quite fully extended) with the ball of your foot on the pedal and sat on the saddle.  If your saddle is too low, pedalling will be harder work and put more strain on the knee joints.  The handlebar height will depend on your riding style - for sporty riding or off-road control you will want a smaller frame offering a lower hand position, so long at the reach isn't too short and your riding style is not cramped.  For more leisurely cycling you may prefer a slightly larger frame with the handlebars a little higher for a more upright position - so long as the frame is not so large that you have to over-reach and that you still have safe top-tube clearance.

Folding Bikes have much more adjustment than normal bikes and so are designed for most adults "one size fits all"





Bike SizingRough guide to calculating frame size


You can calculate the size of frame that you require by measuring your inside leg - crotch to floor - then depending on the style of the bike, from your inside leg measurement;


  • Touring, Hybrid or Leisure Bike (Including Mountain Bike for leisure riding) - subtract 9" or 23cm
  • Road Bike - subtract 10" or 25cm
  • Mountain Bike used for off-road riding - subtract 12" or 30cm


This will give you an idea of the correct size of bike for you - your style of riding may prompt you to go up or down one size.  You can also use the table below:




Bike Size Guide (Table)

Mountain Bikes
Bike Size
Rider Height (feet & inches)
Rider Height (cm)
15" - 16" 5'2" - 5'6" 158cm - 168cm
17" - 18" 5'6" - 5'10" 168cm - 178cm
19" - 20" 5'10" - 6'1" 178cm - 185cm
21" - 22" 6'1" - 6'5" 185cm - 193cm


Commuter / Leisure / Trekking Bikes
Bike Size
Rider Height (feet & inches) Rider Height (cm)
15" - 16" 5'1" - 5'5" 155cm - 165cm
17" - 18" 5'5" - 5'9" 165cm - 175cm
19" - 20" 5'9" - 6'0" 175cm - 183cm
21" - 22" 6'0" - 6'3" 183cm - 191cm


Touring / Trekking Bikes
Bike Size
Rider Height (feet & inches) Rider Height (cm)
15" - 16" 5'1" - 5'5" 155cm - 165cm
17" - 18" 5'5" - 5'9" 165cm - 175cm
19" - 20" 5'9" - 6'0" 175cm - 183cm
21" - 22" 6'0" - 6'3" 183cm - 191cm