Bike Sizing Guide


In Sir Chris Hoy’s Foreword to Phil Burt’s superb book on Bike Fit, Bike Fit – Optimise your bike fit for High Performance and Injury Avoidance (published by Bloomsbury) Sir Chris says how much he loves seeing so many people out on their bikes but that few things frustrate him more than seeing someone riding a poorly set up machine. We completely agree. We’ve lost count of the number of perfectly fit cyclists who have bought a lovely (and often expensive) bike but who haven’t been fitted correctly. They have often been set up incorrectly or in some cases, not even had their cleats on their shoes fitted correctly.  As a result, they are sore, uncomfortable and increasingly unhappy. Worse, they are falling rapidly out of love with their bike and the wonderful sport of cycling. The good news is it is completely avoidable and that is why we have written this bike sizing guide. Criterium Cycles will always recommend that whatever you buy there are significant advantages to having those items professionally fitted. Criterium Cycles trained technicians understand we all come in different shapes and sizes. We know how to make sure you are fitted correctly and comfortably despite those differences. You can read more about our Precision Bike Fit services by clicking on the link.

Buying bikes online

We equally understand that many cyclists are experienced purchasers of cycle equipment. Perhaps they simply don’t have the time to arrange a detail fitting session. We have therefore included a simple method by which you can calculate your inseam measurement for any brand of road bike. We have also included all the size charts for the entire Trek range of bikes, whether road, mountain, hybrid, city or urban. If you have any questions or concerns, then please don’t hesitate to Contact Us. We will do our very best to answer any question on bike sizing you may have.

General Method – Inseam (for all makes of Bike)

To determine your approximate frame size, then the best starting point is to first measure your inseam. Your inseam measurement is pretty much the same as your inside leg measurement. To calculate your inseam and from that calculate your frame size, follow the simple instructions below. It is really important to calculate your inseam measurement as accurately as possible. Otherwise it may result in a wrong frame size calculation. To do it properly really requires a partner or colleague to help and then follow this simple process below:

  1. You will need a tape measure and something with a level edge, say a large spirit level or a clipboard.
  2. Remove your shoes (really important!) and stand with your back against a convenient wall.
  3. Place your spirit level or clipboard between your legs with the one edge square against the wall so that it acts as a set square.
  4. Raise the Spirit Level or clipboard all the way up whilst maintaining the set square effect against the wall. You don’t want it to be painful but you are aiming to bring it up to your sit / pubic bone.
  5. Ask your partner or colleague to measure the distance in cm carefully from the top of the spirit level or clipboard to the floor.
  6. You now have your inseam measurement.
  7. Take your inseam measurement and multiply by 0.657 to derive your frame size.

Road Bikes (General)

These are the bikes where fit is more critical. There is an obvious reason for this on a road bike. You are going to find yourself adopting a number of fairly static positions for relatively long periods of time. Depending on the terrain or the performance you are seeking at any moment in time you may be utilising different positions of your hands on the bars. Occasionally, you will be out of the saddle for that particularly lung busting climb. But road cycling is not as dynamic in terms of your movement as mountain biking. It is therefore critical that for comfort and performance over long periods, your fit is optimised as much as possible.

We have also include Cyclocross Bikes in general advice on Road Bikes because they share many similar characteristics to road bikes but with altered geometry to cope with the demands of Cyclocross.

Mountain Bikes (General)

Mountain Bikes are not quite so critical to determine the precise fit measurement. Body movement is much more dynamic because of the terrain involved. Watch any mountain biker at any level of technical ability or experience – to a greater or lesser degree they will be bobbing around a fair amount. Let’s face it, that’s part of the fun!

That doesn’t mean sizing doesn’t matter because it does. It just means that we can cope with a little more latitude than the precision required for road bikes.

Hybrid, City & Urban Bikes (General)

The vast majority of Hybrid, City & Urban Bikes (like Mountain Bikes) have frame sizes measured in inches. Some are different and are measured in centimetres as for road bikes. If so, you will see that clearly stated on the individual product description of the bike’s specific page on this website.

Kids’ Bikes (General)

Kids’ Bike sizing is generally driven by the height of your child. Check out the various tables below for Trek and Frog to identify the bike size that’s best. If you fall across two sizes or have any concerns / questions, then do Contact Us and we’ll make sure we give you the best advice we can.

Bobbin Bikes

Bobbin Brownie

Bobbin Brownie Size Chart

Bobbin Birdie and Bramble


Bobbin Blackbird, Black Orchid and Luna


Bobbin Noodle, Dark Star and Scout


Bobbin Mino Velo


Bobbin Folding


Frog Bikes

  Minimum inside leg

in cm (ins)

Approx Age Wheel Size Frame Size
Tadpole 32cm (12”) 2 – 3 12”
Tadpole Plus 38cm (15”) 3 – 4 14”
Frog 43 43cm (17”) 3 – 4 14” 9”
Frog 48 48cm (19”) 4 – 5 16” 9.5”
Frog 52 52cm (20”) 5 – 6 20” 10”
Frog 55 55cm (22”) 6 – 7 20” 11”
Frog 62 62cm (24”) 8 – 10 24” 12”
Frog 69 69cm (27”) 10 – 12 26” 14”
Frog 73 73cm (29”) 12 – 14 26” 16”
Frog Road / Track 58 58cm (23”) 6 – 7 20” 11”
Frog Road / Track 67 67cm (26”) 8 – 12 24” 14”
Frog Road / Track 70 70cm (27”) 11 – 14 26” 17”

Trek Bikes

The inseam measurement is sufficient to establish approximate frame size for road bikes. However, for Trek Bikes, if you also know your overall height, you can use the tables below to further refine the most appropriate frame size depending on the particular model you are looking at.

Trek Road & Cyclocross Bikes (Madone, Emonda, Domane, Silque, Lexa, Boone & Crockett)

Trek Bicycle Road Sizing Guide

Trek Road & Adventure Bikes (Crossrip, 920, 720 & 520)

Trek Road (Crossrip & Adventure)

Mountain (Marlin, Skye & 820)

Trek Bike Size Guides - Mountain (Marlin Skye 820)

Mountain (Top Fuel, Procaliber, Superfly, X-Caliber, Cali, Remedy, Fuel EX, Lush, Stache, Farley & Slash)

Trek Bike Size Guides - Mountain (Top Fuel Procaliber Superfly X-Caliber Cali Remedy Fuel EX Lush Stache Farley Slash Ticket)

Mountain (Session)

Trek Bike Size Guides - Mountain (Session)

Dual Sport Series

Trek Bike Sizes Guides - DS Series

City (FX, Neko & Conduit+)

Trek Bike Size Guides - City (FX Neko Conduit+)

Trek Bike Size Guides - All Kids

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