Road Bike Sizing Guide

When you choose the right bike size, what you’re really doing is outfitting yourself for comfortable, pain-free riding enjoyment. 

Road bike sizing can vary significantly among brands, which is the main reason for finding your bike size before you buy. A bike that’s a perfect fit also helps you ride more efficiently, avoid injury, and simply makes riding more fun. Understanding what affects bike sizing will not only help you choose wisely but will give you more control over how to fine tune your fit.  

It’s worth it to invest a little time now in learning how to size a road bike – especially if you plan on buying a bike on the internet – so that your next purchase is a bike that fits you perfectly. 

What you'll learn through this road bike sizing guide:

The anatomy of a road bike frame and its geometry to have a theoretical comprehension of all the parts of the frame How to determine your reach and stack What's your proper height with our road bike height size chart How to adjust your road bike and dial in your position

What's the anatomy of a road bike frame? 

From a distance, a road bike frame looks like two triangles stuck together to form a sort of diamond shape.

Most every road bike has the same anatomy, which consists of: 

Top tube 

This tube runs parallel to the ground between the seat and handlebar; however, it may be sloped (we’ll get into that later). 

Head tube

This is the short tube at the front of the frame, which connects the handlebar to the fork. 

Down tube

As the name suggests, this is the long tube that runs from the head tube down to where the pedals are. 

Seat tube

This tube runs from beneath the saddle down toward the pedals. It is not to be confused with the seat stays

Seat stays

Two thinner tubes that run down both sides of the wheel from underneath the saddle and end at the hub. 

Chain stays

Two thin tubes that run parallel to the ground on both sides of the wheel hub to the pedals. 

A road bike’s fork isn’t part of the frame, but it does complete the basic structure for a road bike, which is why a frame and fork together are referred to as a frameset. 

Road bike frame geometries 

Up close, two road bikes side by side can appear radically different because they possess different tube shapes and because they feature one of these three frame geometries: 

Traditional

Once the only style of frame, you’re more likely to see a traditional frame – with its arrow-straight top tube – as a collector’s item, perhaps hanging on the wall of a bike shop.  

Compact

Three clues that reveal a compact frame are its: sloping top tube; smaller rear triangle; and shorter wheelbase (this is the distance between the two wheel axles). 

Semi-compact

The giveaway here is a more subtle sloping top tube however the difference between a compact and a semi-compact frame may be hard to spot. 

In your search for a properly sized bike, it’s important to point out here that compact and semi-compact frames have two top tube lengths: the actual length of the sloping tube and the effective top tube length, which is the distance in a straight line from the center of the head tube to the seat post.  

This matters because this will affect the bike’s reach, which is the horizontal distance from the center of the bottom bracket to the center of the head tube. 

How to determine your ideal reach and stack 

• Bike fit by a professional – A professional bike fit by a skilled and experienced fitter will either be able to tell you your ideal reach and stack outright or will yield data that will lead to frame recommendations based on your unique measurements. 

• Online bike fit calculator – Since reach and stack both refer to precise measurements based on an XY axis that exists in space – you would first need concrete points of origin (bottom bracket, head tube) from which to measure reach and stack. To arrive at a recommended reach and stack if you’re in the market for a new bike, you’d be best served by first conducting an online bike fit and working backward from the results. 

Why people use reach and stack  

When so-called frame “standards” and new materials started to radically evolve frame designs, old methods for sizing bikes became unreliable.

Reach and stack thwarted frustration by introducing a new way to calculate frame specifications without actually measuring the frame. Reach and stack define an X and a Y axis using the center of the bottom bracket, and the center of the head tube’s top to measure the vertical distance and the horizontal distance between these two points.  

In an industry that has handicapped itself with proprietary sizing, reach and stack seem to be universally accepted as precise and unalterable frame measurements. You’ll often see reach and stack numbers listed in a bike’s sizing data and, if you know your ideal reach and stack, you can get a bike that’s close to a custom fit without paying a custom price. 

However, there’s an easier way to find the right bike size, and it starts with the road bike height size chart

Road bike height size chart 

Many road bikes adapt general sizing to rider height. Sizes are often expressed in standard XS-S-M-L-XL and/or seat tube lengths (i.e., 52 cm = small; 58 cm = large).  

Universal road bike size charts can take the guesswork out of narrowing down your choices.

Standover height 

However, to really zero in on the correct bike size for you, compare your height with the recommended sizing for the specific model you’re looking to buy.  

Despite efforts to standardize road bike sizes, every rider is different and will therefore have different fit requirements.

The distance from the ground to the top of the top tube is known as standover height, which matters to a rider who has short legs – especially when he/she comes to a traffic stop.  

You should be able to stand over the bike with your feet flat on the ground and have about 2.5 cm (1 inch) of clearance between you and the top tube. To be more precise, measure your inseam and add 2.5 centimetres to the bike’s standover height to make sure you have enough clearance. 

Women’s road bike size charts 

While women’s bike sizes are still expressed in universal terms, some brands have completely overhauled the frame design using women’s body dimension data to produce bikes specifically for women.  

It wouldn’t hurt to do a little investigation into brands that claim to supply bikes for women. That said, a lot can be done to a unisex frame to make it supremely comfortable for the rider no matter the gender. 

How to adjust your road bike and dial in your position  

It’s no surprise that a properly adjusted bike will yield a more enjoyable cycling experience and even reduce the chance of injury. If you adapt yourself to the bike instead of adapting the bike to you, over time even the smallest misalignment can cause biomechanical problems that can be frustrating and time consuming to solve.  

There are three contact points between you and your bike: saddle; handlebar; and pedals, which can cause a world of hurt if you’re not dialed in to them.

Here are some tips for getting the fit just right. 

• Saddle angle – level is best. 

• Saddle height – start with a baseline height and fine tune it from there. 

• Saddle position – Knee alignment (not reach!) is key to avoiding discomfort or injury. 

• Handlebar and cockpit angle – the transition from the handlebar to the lever hoods should be smooth and pointing slightly upward.  

• Stem length – Don’t be afraid to swap! 

• Cleat positioning – Center the cleat front and back to the largest portion of the shoe toe box. Before you get to this point though, let’s walk it back a few steps to explain the different types of pedals. 

There’s more to these tips in the full version of Bike fit 101: How to Adjust your Bike and Dial-in your Position. 

Have any doubts? Consult an expert 

If this is your first bike purchase (or maybe even your fifth) and you’re still left with questions, there’s a lot to gain from speaking with an expert – someone who exists in the world of bikes and knows all the ins and outs (plus the quirks, hidden knowledge, and frustrations) of road bike sizing.  

The way to resolve your doubts is by booking a video call with one of Cycling Avenue’s expert advisors. You can choose the one who best suits you for a 20-minute chat to answer all your size questions.  

Here’s how it works: 

1.Choose an advisor and a time slot that works best for you. 

2.Answer a few quick questions on your level of cycling experience. 

3.Your consultation is confirmed! At the time of your meeting, you’ll join using a Microsoft Teams link provided by Cycling Avenue.  

Stick to your needs

Prioritize the right bike size when shopping for a bike and get more value out of it when you enjoy pain-free riding. Entire industries have sprung up around the topic of bike size and they offer products and services that capitalize on your goal to get a properly fitting bike.  

Or you can just start here and take advantage of some free advice with the same primary goal, which is to put you on a bike that fits you perfectly.