Road bike size guide: how to choose a frame size that fits

Bike fit is one of the key things to get right when choosing a new bike. You’ll be much more comfortable and lessen the risk of injury if you’ve got your road bike size right and have your bike set up to fit your own requirements.

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We’ve loads of experience of bike fitting here atCycling Weekly, with a hub linking to all ourbike fitting advice. So here’s a summary of our best advice on how to choose a bike that fits you.

Read the maker’s size chart

If you’re buying a new bike, you need to make sure you’ve got the right size frame. Bike makers will make a bike in several sizes; at the minimum there may be five or six, usually labelled either in cm or from small to large. But in some cases there will be dozens of size options or you might be able to choose a totally bespoke build to your own measurements.

Road bike size guide

A good starting point when choosing your bike size is the brand’s website. There’ll be a size chart for each model somewhere. This will include a geometry chart that lists out all the dimensions of each model in the different sizes offered. It’s pretty complex, but usually includes a recommended rider height range for each size.

If your body shape is pretty average and you sit in the middle of a size range, this might be enough to home in on the size frame that will fit you. If you’re on the cusp between different sizes, it’s usually best to go for the smaller frame size; there’s enough adjustment in a bike’s bar and saddle height and the saddle’s fore/aft position that you should be able to set the bike up to be comfortable.

The importance of reach and stack

Key dimensions to get right are the reach and stack of your bike frame. The reach measures how long horizontally the frame is from the middle of the crank pivot to the top of the head tube, while the stack measures the vertical distance between these two points.

So these are defined measurements that you can use to compare different bikes and select the right sized frame for you. We’ve a lot more detail onreach and stackand other elements of a bike’s geometry and their effects on how a bike will fit and ride.

Cannondale SuperSix Evo 2019

Your optimum reach and stack will depend on the type of riding you’re doing. A race bike frame will typically have a longer reach and a lower stack, to put you in a lower, more aero position, while a bike geared towards endurance riders will have a shorter reach and higher stack, so that you ride in a more upright position.

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If you’ve had a pro bike fit, you’ll have an idea of the optimal range of reach and stack to look for, which you can use to shortlist models and sizes that should fit you. It’s worth bearing in mind that a very racy position might not work for you - we’ve asked whether you really need a positionas aggressive as the pros.

Get a professional bike fit

The best way to be sure that your bike will fit you and that it’s set up right is to invest in a professional bike fit. A bike fitter will spend several hours with you, setting you up on a test bike indoors and having you ride it as they adjust the position of your saddle, bars and other components, to see how these changes affect your riding.

road bike size

It’s a process that usually costs a couple of hundred pounds, but will ensure that you’ve got the right dimensions to fit you. You’ll come away with a list of measurements that you can use to zero in on the best road bike and size to suit your needs. And it should be portable if you decide to swap bikes or buy another one in future.

It’s worth bearing in mind that your optimal fit may change over time, as age, weight and flexibility change. So we’ve advice on why you might want toget your bike fit recalibratedand somecase historiesof people who’ve benefited from a new bike fit.

Many bike shops will offer bike fitting services. It’s worth asking if you can get a fit as part of the process of choosing a bike, if you’ve already decided on a bike shop that you want to use to buy your next bike.

We’ve a post onwhat to expect at a bike fit and recommended fitters in the UK.

Do it yourself

If you don’t want to spend your cash on a pro bike fit, there’s plenty you can do on your own, as we explain in our postDIY bike fit: how to set up your bike, which also sets out some of the pitfalls of doing your own fit.

saddle height

Check your saddle height is correct to avoid injury
(Image credit: Andrew Sydenham)

A key measure of road bike size is your saddle height. You can work this out roughly by using the LeMond formula: measure your inside leg length and multiply this by 0.885. You can also do it empirically by setting your saddle so that you can place the centre of your foot on the pedal with your leg straight.

We’ve more advice from the experts onsetting saddle heightand what to do if you’re suffering fromknee pain- a common symptom of incorrect saddle position - including some exercises to help.

Swap out your components

Still not comfortable on your bike? We’ve had a look atsaddle comforttoo. It’s one of the main contact points between you and your machine, and the most personal. It’s possible a swap-out from your bike’s stock saddle will help. Again, it's something a bike fit can help with.

Specialized Power MIMIC women's saddle

Reach to your bars may also be a factor if you’re suffering from discomfort in your shoulders, back, neck or hands. We’veadvice on what to doand on how toset and adjust your bar heightto suit you.

Seek advice on your road bike size

Above all, when selecting a new bike or if you have fit problems or discomfort, we’d recommend asking for advice from an expert. That might not come free, but it should be worth the expense to up your riding enjoyment, avoid injury and ensure that you’re getting the most from your cycling.