How To: Choose the Right Bike Size

Kinesis Racelight

Whether it is your first bike, you have an on-going irritating pain or you are looking for optimum performance, getting the right bike fit is essential. How to choose the right bike size is a topic that most people know very little about and long gone are the days where your height was enough to measure you up for your new bike. Bike fitting has become quite a skilled profession and there are many trained bike fit specialists available nowadays. But don’t feel too daunted reading this, most people only need a little tweak here and there to get that optimum riding position.

It is quite expensive to seek out a professional so great if you have but if you haven’t got money to spare and are looking for simple easy steps to get a ‘perfect’ fit then we are here to help with a few essential pointers.

Top tips to choose the right bike size:

  1. Measure your height to find a frame

    Bikes come in all different sizes, and when it comes to buying one you need to make a number of measurements before you choose. It’s not like you look at it and think, ‘yep that looks big enough for me’ – there are several dimensions that you need to consider. Bike frames are not one-size-fits-all, in fact bike frame size varies according to a few key measurements:

    Height: you need a precise measurement in order to size yourself accurately. The best way to do this is to stand straight with shoulders back against a wall (in just your socks or barefooted) and pencil a mark on the wall in line with your head – it’ll be easier if you get a mate to help you. Then use a tape measure to get your height in cm’s or inches.

    Armspan: again, measure this against the wall, tilting sideways. Put the tip of your fingers of one hand just touching the floor, and reach up the wall with the other arm, making a mark where the tip of your fingers are again. Allign this measurement with your height – if it is slightly longer, then consider getting a larger sized bike and if shorter, consider a smaller size bike.

    Inside leg: all you need to do is measure the distance from the floor to your crotch standing with legs shoulder width apart as though you would stand over your bike.


  2. Check it's the correct fit!

    If you have a turbo trainer this is ideal, this way the bike is unable to move and the bike fit is made easier.

    Make sure the bike is on a flat even surface and have the front end raised to ensure the axles are at the same height, it’s no good starting with a wonky bike! Remember to pump up the tyres!

    We suggest first of all to find someone of a similar height to you that has a bike you can sit on or pop into a bike shop to try a few sizes. A simple gauge to test the sizing is right is by standing over the bike as if you are going to sit down, but keep your feet on the floor. What you’re looking for is the clearance between your crotch and your bike’s top tube. If you have a couple of inches clear then you have yourself the correct fit as you will be able to mount on and off your bike with no problems.

  3. Sit on the bike to assess your Saddle Height

    Next thing is to determine your saddle height. This is very important so you get the most out of your pedalling. Too low and you could develop cramp, tight legs, burning sensations and loss of power. Too high and you also will suffer from loss of power and incorrect pedalling as the heel will be raised to compensate for the saddle being too high potentially causing cramp and unnecessary joint problems.

    Determining your saddle height will ultimately decide the size of the bike you need if you do not know what length of top tube you need. The size of a bike is measured from the top tube so finding this measurement will help you choose the right size in the future.

    Before climbing on make sure the saddle is perfectly level and not titling forwards or backwards and fit in the saddle in the centre of the rails. Climb on the bike and hang both legs free, make sure the pedals are at 12 and 6 o’clock. Place your heel on the pedal, at this point you heel should just reach the pedal. If you can’t reach it with your heel your saddle it’s too high. If you can comfortably rest on the pedal the saddle is too low.

  4. Adjust your Saddle Position

    Just one more thing to make sure is adjusted correctly is the position of the saddle. This needs to be centred to suit your body. You may need a little helper here… Making sure the cranks are horizontal your knee should be in line with the centre of the pedal axle. This will help to realise where your saddle should be positioned on the seat post.

  5. Reach for the handlebars to check their position

    Once this is set to the perfect position, clip into the pedals and get in the ‘riding position’ your hands should be able to reach the hoods of the handlebars comfortably with a slight natural bend in the elbows and your back at approx. 30-40 degrees, depending on the type of riding/racing you are wanting to do. If you are on your own a good way to gauge this is to look down over the front wheel and if you can just see the front axle then this is not far off. If you can see too much off the axle chances are the top tube is too short. At this point see how much seatpost you have showing. If there is more than 10 inches the chances are the bike is too small, vice versa if there is only 3 or 4 inches showing the bike is potentially too big.

    This of course is a guide as all people are different shapes and sizes so if you are between sizes then little tweaks to the stem and saddle can help if you have exceptional long arms or legs etc!

    Stand over height can also be another guide if you are struggling to find the perfect size. Approx 2 inches is a good indication.

  6. Check the Stem Size

    Of course the stem size does come into this so ensure that you are using a bike with a standard 120mm stem on it so not to throw the fit out. If you have unusually long or short arms then this can be adjusted to suit. A guide is to sit on the bike resting your hands on the hoods of the handlebars and look down at the front wheel, If you can just see the axle then the stem is the right size for you. You may need to try anything forma 90mm-140mm stem. But it is most common to use around a 120mm stem. I would question if the bike is the right size for you if you have to go to extreme measures, but in some cases cannot be avoided.

  7. Change your Cleat Position

    Finally your cleat position, don’t neglect this as it can throw out the whole fit of your bike. It’s important to not neglect the simple things. Do your cycling shoes fit? Too big, too small and this will throw out the whole fit.

    Once this has been established make sure the Cleat position is set up to get the best pedal symmetry and power transfer whilst avoiding hip and knee injuries, the simple way to explain is to place your feet flat on the ground and locate the ball of your foot by finding the bony part of your foot and drawing a mark on the underside of the shoe to mark it. Get your cleat and aligning up your mark so that its sits where the centre of the pedal axle will be. This will find the optimum position for your cleats. Finding the right angle may take a few tests as you will need to find your natural angle but this can be played around with once you feel comfortable. You can buy bike pedals and cleats here from PBK.

So before buying the bike of your choice, make sure you get hold of the geometry of the bike you fit to yourself and match up the top tube measurements. Where you may be a 50cm in one make of bike you may be a 53cm in another as all manufactures measure their frames in different ways. As long as this all feels okay and you are happy. Measure the top tube, and saddle height of the bike and this will help you choose a bike that is the right size for you.

For more detailed information on how to fit yourself on a road bike, read through our Bike Buying Guide which tells you everything you need to know about the bike buying process.

Elizabeth Demetriou

Elizabeth Demetriou


I'm a runner at heart but since shin splints became a big part of my life, I turned to cycling as a form of cross training. I love riding track and am a regular on the Manchester velodrome; on the road I ride a Trek Lexa and I call it Toby.

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