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When buying a full size bike it is of the up most importance to buy a bike that fits you. Riding a bicycle that does not fit you can be uncomfortable, dangerous or even cause injury. Some potential disadvantages of riding a bike that is the wrong size are:

  • Cause pain and/or injury
  • Inhibit pedalling technique that can result in you being less efficient
  • Is less comfortable and therefore less enjoyable

The chart below is a general guideline of the sizes for both Mountain and Road bikes. There are various brands that have different size frames, so for accurate results please ask a professional at any bike store.


Bike Size Chart

Bike Size Chart


Generally the size of a bike is measured from the centre of the chain set (the object the pedal arms are attached to) to the top of the frame at the point where the seat post is inserted. Again this is not a universal standard and some manufacturers measure their bikes to the centre of the intersection of the top tube and the seat tube, altering the sizing. There are some rules of thumb that can be applied when trying a bike for size. See table below for more information.


Choosing The Right Size Bike

BMX Bike

One standard size applies to all

Hybrid Bike

Standing flat-footed on the ground, you should have a minimum of 2.5cm clearance between yourself and the top tube of the frame

Mountain Bikes

Standing flat-footed on the ground, you should have a minimum of 5cm clearance between yourself and the top tube of the frame

Road Bikes

Standing flat-footed on the ground, you should have a minimum of 2.5cm clearance between yourself and the top tube of the frame


In some instances it is not possible to measure the size of the frame yourself. The simple calculation below can help to estimate your required frame size.

  • Take your inside leg measurement to the floor
  • Subtract 5cm for mountain bikes, or 2.5cm for road bikes
  • Subtract 23cm, the average distance from the bottom bracket to the ground

Using these rules will give you the maximum frame size that you will need.

Bear in mind that buying a bike of the correct size is not just about having the correct height measurement, as the bike’s height changes so too does its length and distance from the saddle to the handle bars. On average for every 5cm the bikes frame increases the distance from the seat to the handle bars increase 2.5cm. This means that even if you are able to stand aside a taller bike you may not be able to comfortably reach the controls on the handlebar. Most seats on bikes can be adjusted, usually by 10cm-25cm allowing the bike to be tailored to fit you.

As we are all different shapes and sizes, finding the right size bike and getting the right position set up on the bike can be quite difficult. The above information should start you off in the right direction, however advice from a professional who can physically see you on the bike and adjust your position is the best way to get a perfect fit.

If you intend to ride long distances (30km or more) or race your bike, having the correct size bike becomes even more critical. Usually these types of riders are riding the bike longer amplifying any potential problem which can result in serious injury.

The more upright the riding position the less crucial it is to have the exact fit. Hence why just a few sizes in mountain bike sizes can cater for most of the adult population. In comparison to race bikes that demand efficiency over comfort, the perfect size and position are much more important and is the reason why the size of race bikes can vary by just a few centimetres.


Buy A Trusted Brand

Lastly, buy a good brand. Although what brand you buy often comes down to your budget, the better brand bikes generally have increased performance, are safer and durable.


It is recommended that someone who is doing long rides or riding race bikes be fitted by a professional. To find a bike shop in your area click here

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