Bike Size Guide
Bike sizing can be complicated, so use this bike size guide to help you find the right size of bike for your needs. Riding the right sized bike will make cycling more enjoyable and comfortable, as well as allowing you to get much more from your new bike.
To work out which size bike you need, use the downloadable bike frame size guides at the bottom of this page. These guides give detailed frame size tables for bikes sold at Halfords.
Before you use the tables, it will be useful for you to know which size to look for, so read on to learn how bike sizing works and how to choose the one for you.
How Are Bike Frames Measured?
The length of the seat tube determines most bike frame sizes, measured from the middle of the bottom bracket to the top of the seat tube, where the seat post goes into the frame. Use the frame diagram on the right for help identifying these parts.
However, some bike frames are measured from the middle of the bottom bracket to the crossover of the top tube and seat post. Also, some road bikes are measured horizontally between the centre of the head tube and the centre of the seat tube.
This can cause some discrepancy in sizing, so look at individual product pages for more details or model-specific sizing diagrams to be certain. If in doubt, do not hesitate to contact your local store for more advice.
Key to Frame Diagram
TT = Top Tube
ST = Seat Tube
HT = Head Tube
BB = Bottom Bracket
How To Choose The Right Size Bike for You
For new cyclists, the best place to start is by measuring your height. Stand barefoot on the ground with your back against a wall. Use a book to mark your height against the wall, and measure the distance from the ground to your mark in feet and inches.
If you are bridging two different frame sizes, the deciding factor is usually your reach. To find out whether you have a longer or shorter reach, you should work out your "ape" index. Measure your arm span and subtract your height: if the result is a positive number, try the larger frame size first, if the result is negative, then instead try the smaller frame size first.
When trying out new bikes, you should make sure you have the right amount of clearance over the top tube. For mountain bikes, this should be a minimum of 3 inches when you stand flat-footed on the ground. For road bikes there should be a minimum of 1 inch, unless the bike has a sloping top tube, when there should be between 2 and 3 inches.
Ladies Bike Sizing
The range of bikes at Halfords includes many women's bikes, reflecting the increasing number of women who are interested in the sport. Women generally have different proportions to men, and so their bikes are built with slightly different geometry.
Typically speaking, women are shorter and lighter than men, and have shorter arms relative to their legs. They also tend to have smaller hands. Some, if not all of these are reflected in the design of women's bikes.
Ladies bikes have a slightly shorter top tube relative to the rest of the bike to account for proportionally shorter arms. This allows the legs to reach full extension whilst still being able to reach the handlebars. The other main difference to the frame on women's bikes is that they tend to have more clearance over the top tube, allowing you to mount and dismount comfortably.
Other differences can include female-specific saddles and brake levers that are closer to the handlebars to allow for smaller hands and handlebars that are smaller in width to reflect narrower shoulders.
Bike Frame Size Guides
The following .pdf files contain bike frame size tables for the bikes sold at Halfords.
Road Bike Size Guide
If you are considering a road bike, look at our road bike size guide, which includes information on compact, semi compact and standard frames, as well as sizing of female-specific road bikes.