Cyclocross bike sizing guide

Getting the right fit on a cyclocross bike is crucial to make riding comfortable and safe. Cross bikes are the perfect go-anywhere and do-anything adventure machines. In our cyclocross bike sizing guide, we provide some expert advice that will help you choose the right CX bike for you. The information here is relevant for all riders.

How do cyclocross bikes differ from road bikes?

Before we get into the numbers, it’s worth exploring the differences between road bikes and cyclocross bikes.

Road bikes are built to go fast, with an aggressive frame geometry that compels the rider to lean forward and adopt an aerodynamic position on the bike. Cyclocross bike frames are designed to keep the rider a little more upright. This makes them more comfortable for longer journeys and suitable for navigating obstacles such as tree stumps or other road users!

Where carbon road bikes are the most popular choice, cross bikes are still built primarily from metals, with aluminium and steel popular options.

Finally, cyclocross frames have larger clearances around the wheels to accommodate larger tyres and to stop them getting clogged up with mud during off-road rides.

Cyclocross bike size basics

Riding the correct size bike is essential for your performance and your physical health. Ride a bike that’s too small for you and the cramped position will limit the power you can deliver to the pedals and can cause stresses and strains. Ride one that’s too big, and you’ll also be underpowered, but you can also find handling difficult – which can be dangerous.

There are three fundamentals that you need to know when selecting the right bike:

  • There should be 2 inches (approximately 5cm) of clearance when you stand over the bike with your feet laid flat against the floor.
  • You should be able to pedal comfortably with a slight bend in your knee at the bottom of each pedal stroke (left and right legs).
  • You should be able to steer comfortably and reach both brake levers.

Cyclocross bikes, like all other cycles, use seat tube length to size up bikes. The measurement may be in cm (like road bikes) inches (like mountain bikes) or in sizes (small, medium, large and extra-large).

How do I choose the right size cyclocross bike?

It’s time to get measuring. You’ll need three measurements:

  • Your height
  • Your inside leg measurement
  • Your reach


Some manufacturers will specify a frame size according to your height. It’s a crude approach, but if you’ve owned bikes by the manufacturer before, it may be enough information to help you choose.

Inside leg measurement

You inside leg measurement is used to figure out your standover height. This is the distance between your crotch and the top tube of the bike. As we’ve explained above, aim for at least 2 inches, and you’ll be able to jump on and off your bike easily.


Your reach is crucial as it can help you decide between bikes if you’re stuck between sizes.

To do so, use the Ape index. Measure your arm span by stretching your arms as far as they can go and get someone to measure the width. Subtract this figure from your height. If your arm span is greater than your height, go for a bigger sized frame. If it’s less than for the smaller one.

Science v Feel

Sometimes we can get bogged down in numbers, but riding is all about feeling, so there’s no comparison for jumping on a bike and taking it for a test ride.

Manufacturers can differ in their frame sizing, so just because you ride a small frame road bike, it doesn’t necessarily mean you’ll ride a small cross bike.

It may be that you need to make some alterations and upgrades to your bike to get the fit perfect. Simple modifications include fitting a different saddle, replacing the stem or swapping to narrower handlebars.

Replacement cyclocross parts are readily available, easy to fit and inexpensive, which means you can experiment until you get things right.