How could I possibly look happy after riding 104mi on my bike? Because my bike fits my body! It’s not only the correct size, but I chose a bike that had dimensions that accommodated my longer legs and short torso! If you’re thinking about getting a new bike, I cannot stress enough the importance of getting one that is correctly sized.

One of the most important aspects of a road bike is the fit! No matter how great the componentry, how brand new the carbon fiber technology is, or how aerodynamic your setup is, you will be in for a rough time if the bike is too large or too small. And this is true whether you are the weekend warrior, ride occasionally for fitness, or are trying to finish on the podium of your local crit. This also applies to mountain bikes and hybrid bikes alike! Although this article focus on road bikes, regardless of the type of bike you're looking to purchase, these same principles can be applied for a perfect fit.

Finding the right size road bike can be no sweat at all. This article will equip you with the knowledge you need to confidently select the right-sized road bike, so you can fly down the road for miles and miles.

Terms and Disclaimers

Now, before I dive into teaching you how to pick the perfect-sized road bike, I must mention this disclaimer. Not all bikes are sized the same. A “medium” in one brand may not be in another (I too think this is silly). Why can’t we make some standardized system across the industry and manufacturers? Additionally, if you’ve been in the market for a road bike, you may have noticed that most road bikes are sized in centimeters. Depending on the manufacturer, this may refer to the top tube length or the seat tube length, which are pictured here below. The top tube is the tube running across the top of the bike that connects the top of the seat tube to the top of the head tube. The seat tube connects from the bottom bracket to the top tube, while also supporting the saddle of the bike.

There are also a few other terms that are important to understand prior to selecting the ideal road bike size for you. Besides the effective top tube length and seat tube length, some other important measurements include standover height, head tube length, stack, and reach. You would find this by looking at the bike geometry charts of any given bike online. Bike geometry charts and frame geometries can be really confusing to understand, but the list below will provide you with the perfect base information you need for selecting the right size. Now, this isn’t to discount the importance of other measurements or angles of the bike, but if you understand these few measurements, you’ll be on your way to an excellent bike fit and picking the perfect road bike size. So, what do these mean exactly?

• Standover height: Height of the bike from the ground to the top tube.
• Head tube length: The length of the front portion of the frame where the top tube and down tube meet. This is also what secures the fork, stem, handlebars, and steerer to the bike.
• Stack: The height from the bottom bracket (where the cassette and crank arms are mounted) to the top of the head tube.
• Reach: The length from the bottom bracket to the head tube. This differs from stack as reach measures left to right, whereas stack measures up and down.

Understanding how these few measurements play together and what they mean will lead to an ideal bike fit. But there are also easier methods than getting into the nitty gritty of every centimeter on the bike! Finding the right size bike does not need to be super confusing or complex. All it means is that you have to double-check a couple of things to properly ensure the right size road bike. There are a few methods to finding the right size bike, so let’s dive in on this adventure together so we can get you out and riding around!

First and Easiest Method: Manufacturer Road Bike Size Chart

As we as a society emerged from the COVID-19 pandemic, relying on online purchases more than ever, bike manufacturers are realizing that they need to provide better information to potential customers. Some brands, such as Cannondale and Diamondback, list the size of their bikes as it correlates to rider height on their website. For example, they might state that a 54cm sized bike is ideal for someone 5’7-5’11. Other brands will list their bikes in traditional sizes like medium, large, and extra large (XL). In these instances, a size guide will also be listed, helping you know the exact ranges and cutoffs. For most people, using the manufacturer's recommendation for sizing is just fine. This method is for those who are looking to bike for fitness and fun. But what if you are looking for more than just a little fun? What if you've been a cyclist for a while and want to take your cycling a bit more seriously and ensure that you have a great road bike fit? Or perhaps you fall between the middle of two manufacturer-recommended sizes?

Second Method: Math!

Ah yes, that subject we all know and love. Who doesn’t love doing a little math? But don’t worry, even if you are number-challenged like me, this is easy math. So, how does this break down?

Formula: Your Inseam (cm) x 0.7 = Bike Size!

My inseam (measurement from your crotch to the ground) is 31in. A quick Google conversion tells me that 31in is about 78.74cm. Multiply that by 0.7, and we get about 55. So a good bike size for me would be 55cm! Now, again, this is a 55cm effective top tube. This method can be excellent for dialing in the correct size for you even more! But what if you need something that gives you better than a great fit? What if you need that perfect-sized road bike, where every dimension is dialed into you?

Third Method: Professional Bike Fit

While this option requires quite a bit of effort, it will lead to you getting the perfect-sized road bike. Bike fitting is a process that can be fairly standard all the way to incredibly complex, utilizing high degrees of technology. But regardless of the complexity of the fitting you go for, a proper bike fitting will lead to you knowing exactly what to look for in the dimensions of the bike. Head to your local bicycle shop or bike fitter, and they will set you up on a bike. They will take measurements and photos and adjust the bike as you ride to find the optimal body geometry and comfort, without sacrificing aerodynamics or power. A bike fitter would provide you with the dimensions that you would need in a bike which you could compare to the aforementioned geometry charts. This would lead to the perfect road bike size for you.

Other Considerations

These three methods are fantastic and will put you well on your way to getting the perfect road bike size and fit. But what if you’re like me and have long legs and a short torso? Or maybe you’re the opposite and have very long arms?

Long Legs and Short Torso

If you fall into this category, I would recommend going a size smaller than what is recommended. A shorter torso means that you will have to have a shorter overall top tube and shorter reach on the bike. So although you may be recommended one size based on your height, this wouldn’t exactly be the best fit.

For example, if you use a manufacturer's recommendation and they recommended a 58cm bike but they also carry a 56cm, I would lean towards the 56cm. In this example, to accomomdate your longer legs, you would just adjust the bike saddle height to a point where, at the bottom of your pedal stroke, your knee has a slight bend.

Short Legs and Long Torso

If you happen to have shorter legs but a long torso and arms, you will most likely need a larger size, especially if you’re between sizes. You’ll need a bike that has a longer reach and longer top tube, so if you’re recommended a 54cm solely based on height, a 56cm might actually be a better option! From there, you can make any needed saddle adjustments to perfect how the bike feels while riding.

Little Adjustments

There are certainly more tweaks on the bike that can be made to dial in your fit. You can adjust the fore/aft position of your saddle to move your weight on the bike forward or back. You can adjust your stem length which would shorten overall reach. You can adjust the position of your handlebars, or get wider or more narrow handlebars too! But I would only recommend these changes if recommended by a bike shop because you are feeling some serious discomfort.

Your Goals

One crucial aspect to also consider are your goals with biking. Let’s say, for instance, you are truly between sizes at a recommended 55cm, but the bike you’re after is only offered in 54cm and 56cm. If you are looking for something a bit more comfortable that you are riding for fitness, the larger bike frame size may be the way to go. You can be in a more comfortable and upright position without sacrificing the ability to get a workout in. The larger frame could also be better in the long term, as a more comfortable position will lead to easier rides on the body over a long period of time. On the other hand, if you’re looking for maximizing speed and aerodynamics, the smaller frame may actually be better, keeping you more compact, and reducing your drag.

Final Thoughts

So utilizing all the information I have listed above, let’s walk through an example so you can see how these tips are applicable to finding the right bike size!

I am 5’7 and have roughly average-length arms and legs. We will also say I’m looking at purchasing the Trek Emonda ALR5 (my current workhorse) but am not sure what size I am. First, by visiting the Trek website, I see that for this bike, based on my height and leg inseam, they recommend a 54cm. However, I am relatively close to the border of 52cm as well. I also know that I am someone who feels more comfortable with having a shorter reach, as I don’t like feeling like my arms and wrists are way out in front of me, leading to a more semi-compact riding style. I know this also means I would need a shorter top tube. Taking these things into consideration, I am actually more inclined to go with the 52cm instead of the 54cm, because while it’s perfectly fine to pick a size just based on height, once I start considering other factors, I see that a 52cm would be the best option.

To explore more Cycling articles as you pursue your journey in the sport, check out the Expert Journal here on Curated.