Your bike size is important to get right as, just like shoes, the same size in one brand might be different to another. Too big and you'll fight to stay in control, too small and you'll find yourself with a sore back, bum or knees by the end of a ride.
Unless you know your exact fit, it can be hard to know which bike to go for online, or how to set up your dream bike after buying via the web. If you are in any doubt, go to your nearest dealer, ride the bikes of your choice and benefit from their staff's expert fitting advice.
Adults
For normal adult sized 26" wheels (or 27" or 28" road bike wheels), size is determined by frames size (kids bikes are determined by wheel sizes with appropriate age ranges attached).
Frame size is measured from the top where the seat post slots in, down to the bottom bracket (the centre of the axle carrying the pedal arms). In the UK and USA this is measured in inches, while in Europe it is often in centimetres. Some sizings can be different as manufacturers measure from different places, such as from the middle of the top tube intersection and the seat tube. If in doubt ask the manufacturer where the measurements are taken from, or take a tape measure with you to the shop.
Frame Size Inside
leg (minimum size)
Person Size
22"-23"
32"+ 6ft
+
20"
29" 5ft
10"
18"
27" 5ft
6"
16"
25" 5ft
4"
14"
23.5"
5ft 2"
Sizing your bike
Racing Bikes
Stand flat footed on the ground and look for a minimum of 1"
between yourself and the top frame tube.
Mountain Bikes
Stand flat footed on the ground and look for a minimum of 3" between yourself and the top frame tube.
Can't try the bike for real?
Here's how to estimate your frame size without having to sit on
the bike.
1. Measure your inside leg measurement to the floor (wearing the
shoes you would wear for biking)
2. Subtract 3" for a mountain bike or 1" for a road
bike
3. Subtract 10" (the average distance from the bottom bracket to
the ground). This figure is the maximum frame
size you'll need.
As bikes get bigger height-wise, they also get longer, so make
sure that you can still comfortably reach the handlebars and
manage all the controls. Get a bike too big for
you and it can be dangerously difficult to control. The
distance from the saddle to the handle bars increases by an average
of 1" for every 2" increase in frame size. Saddles are
adjustable by between 4" and 10" and handlebars can be moved
up and down, elongated or shortened so you can tailor the bike to
fit you perfectly.
Kids
Kids bikes are usually grouped into age categories, but there's no need to stick to it rigidly and force your tall 6 year old on to a 6 year old's bike. If your little Johnny or little Suzie feels comfy and not too stretched out while sitting on the bike with the ball of their foot touching the floor, can turn the handlebars without hitting their knees, operate the gear and brake levers with ease, there is nothing wrong with buying a bike from a bigger or smaller age category.
12" Wheel - ages 2½ to 4
14" Wheel - ages 3 to 5
16" Wheel - ages 5 to 7
20" Wheel - ages 7 to 9
24" Wheel - ages 9 to 11
26"+ Wheel - ages 11+ (adult cycles)
When buying 12" & 14" wheel 'first bikes' there are many toys bikes, sometimes cartoon and character branded bikes, which may not feature high quality parts. They often feature plastic brushes instead of steel bearings in the hubs and main cog assembly. Whilst sometimes this works well and spare back up parts are also provided, plastic brushes commonly wear out very quickly. For a quality ride look for bikes that use ball bearings in the hubs and main cog assembly.
Once your little angel has learnt to ride without stabilisers
(often at about age 5) they can move up to a 16" wheel cycle which
are not normally fitted with stabilisers, but they can be added if
needed.
With 20" wheel bikes and above, you start to get different
frame sizes. This gives smaller, confident riders the advantage of
fitting on to a larger wheeled bike. Here it's tempting to buy
little Johnny or little Suzie a larger bike that they can grow
into...which they will, but in the meantime they will find
it a difficult bike to control which can be very
dangerous, particularly where roads are involved.
