What Bike Size Should I Buy?

If you have stumbled across this page, then you’ve probably decided to treat yourself to a new bike. First of all congratulations, your health and fitness is going to thank you for it!

Ordering bikes online is becoming more and more popular because there are lower shop front costs, making bikes even cheaper.  Yet, the age-old question asked by bike shoppers is always, “What size bike should I get?”

This doesn’t need to be a complicated exercise. By sizing the bike for your body and needs, you’ll be well on your way to a more comfortable riding experience.

In this article, I’ll provide information and charts that will help you choose the size of your perfect bike!

Your Body Shape And Type

Find Your Bike Size Measurements

Before we get started, you’ll need to take a few measurements of your body. It’ll be a lot easier if you enlist the help of a family member or friend!

  • Height – If you don’t know your height already, you can measure yourself while standing on a flat surface with your back against a wall. Your feet should be roughly shoulder width apart.
  • Torso length – Your crotch to your sternum (the V-shaped curve below your neck)
  • Arm length – The end of your collarbone to the center of your palm
  • Leg Inseam – Your crotch, (i.e. where the saddle is) down to your foot. Arguably, the most important measurement when sizing a bike is your inseam length. I would recommend being a bit more precise with this one.

Now with these measurements, you can use a free online bike calculator to determine your bike’s size.  You simply input your measurements and the bike type you want to buy. The tool then calculates the perfect size to fit your needs.

If you’d like some extra tips and tricks about sizing your bike, read on!

Body Positioning

When hopping on a bike for the first time, I effectively go through the following mental checklist:

Standover Height

Your inside leg measurement will determine your standover height.  This is the clearance between the top tube of the bike and your crotch when stood just in front of the saddle. Most bike brands suggest a clearance of at least two inches to enable you to hop off quickly as and when required.

Upper Body

Aim for a riding position that doesn’t give you too much strain on the lower back. You should also have a slight bend in your elbows which acts like shock absorbers effectively. You also shouldn’t need to feel like you’re constantly reaching forward.  Think comfortable 🙂

As you continue to ride and improve your strength and fitness, you can adjust your settings so you are in a more aerodynamic position!

Seat Height

This is quite important as it will result in how efficiently you’re pedaling with your major leg muscles. There’s a couple of quick checks that I run to ensure I have the correct seat height.

  1. Standing next to the bike, aim for the bike seat to be roughly in line with your hip bone.
  2. Jump on the bike and with your foot at the bottom of the pedal stroke, you should see a slight bend in the leg (roughly 80% of full leg extension). If there is no bend in your knee, I suggest lowering the seat a bit. This holds true for road, mountain and hybrid bikes.

Seat Fore/Aft Position

When your foot is at the 3 o’clock position of the pedal stroke, your knee should align over your forefoot. In this position, your shin will tilt slightly forward.

A plumb line dropped from the bottom of your kneecap should fall straight to the ball of your foot and through the center of the pedal.

How Bikes Are Sized

Different types of bikes are sized and measured differently and each will have its own nuances – even between brands this isn’t consistent! Below are some general guidelines for each type of bike:

Road Bike

Road bikes generally come in standard small, medium and larges and an associated numerical size (usually in centimetres or inches). Unfortunately, it’s not a easy comparison between brands though. Your measurements might fit a medium Giant bike but feel quite awkward and uncomfortable on a Cannondale bike, so you’ll need to test and adjust accordingly.

Mountain Bike (MTB)

Again, MTBs come in standard small, medium and larges with numerical figures. But, unlike road bikes, they are generally similar across brands.

Yes, they don’t want to make it too easy for us 🙂

Hybrid Bike

As the name suggests, these bikes are a mix of road and MTB bikes.  I generally describe them as a road bike with flat handlebars. As for the sizing of these, I’ve found that they’re a bit more akin to MTB style sizing and there’s not as much variance between sizes.

Bike Wheels

Type Of Bike

Now that you have your measurements, next, you need to decide what type of bike you’re looking to buy (i.e. road, mountain bike or hybrid). If you need some help in this department, check out our beginner’s guide to picking the perfect bicyle.

Once that’s done, the easiest method to calculate your bike size is by using your height.  This will give you a general idea of your frame size, however, it won’t give you a perfect fit. A good second piece of data is the top tube length (see further below for diagram on what is the “top tube”).

Below are some general guidelines for bike sizes depending on your height and the type of bike you’re looking to get. Keep in mind this is only general information and as mentioned, sizing between brands can vary quite a bit.

Road Bike

Road bikes are usually sized in centimetres, or using a Small / Medium / Large system.

Men

HeightBike Size
4’10” to 5’0” (147-152 cm)XX Small (47-48cm)
5’0” to 5’3” (152-160 cm)X Small (49-50cm)
5’3” to 5’7” (160-170 cm)Smal (51-53cm)
5’7” to 5’9” (170-175 cm)Medium (54-55cm)
5’9” to 5’11” (175-180 cm)Large (56-58cm)
5’11” to 6’5” (180-188 cm)X Large (59-62cm)
6’5” or taller (196+ cm)XX Large (62cm+)

Women

HeightBike Size
4’10” to 5’1” (147-155 cm)XX Small (44-46cm)
5’1” to 5’3” (155-160 cm)X Small (47-49cm)
5’3” to 5’5” (160-165 cm)Smal (50-52cm)
5’5” to 5’8” (165-172 cm)Medium (53-55cm)
5’8” or taller (172+ cm)Large (56-57cm)

If your measurements are in between two sizes, then it really becomes a personal choice, but the general rule of thumb is to go the smaller size. All things being equal, a bike that’s a little small is much easier to correct – for example you will be able to raise the saddle.

Here’s a great video on the basic settings you need to calibrate when buying a road bike:

Mountain / Hybrid Bike

From personal experience, I’ve found that mountain / hybrid bikes are much easier to size.  Generally, all you need is your height and your leg inseam length.

Men

HeightBike Size
4’10” to 5’0” (147-152 cm)X Small (13”)
5’0” to 5’3” (152-160 cm)X Small (13-14”)
5’3” to 5’7” (160-170 cm)Smal (15-16”)
5’7” to 5’9” (170-175 cm)Medium (17-18”)
5’9” to 5’11” (175-180 cm)Medium / Large (18-19”)
5’11” to 6’5” (180-188 cm)Large / X Large (19-22”)
6’5” or taller (196+ cm)XX Large (23-24”)

Women

HeightBike Size
4’10” to 5’1” (147-155 cm)X Small (13-14”)
5’1” to 5’3” (155-160 cm)X Small (13-14”)
5’3” to 5’5” (160-165 cm)Smal (15-16”)
5’5” to 5’8” (165-172 cm)Medium (17-18”)
5’8” or taller (172+ cm)Large (19”+)

If your measurements are in between two sizes, then it really becomes a personal choice. But, unlike road bikes, most people generally go the larger size with MTBs. Given the general mountain bike setup, a slightly larger frame helps with comfort and handling of the bike.

In this next section, I’ll cover the different types of bikes in a bit more details when it comes to specifics to look out for.

Road Bikes

A road bike is all about speed and they generally come in two styles. First, the racing road bike which is designed purely for speed and second the sportive road bikes which is designed for a bit more comfort.

The sizing quoted for road bikes is generally for the seat tube dimension (diagram below for reference). Along with the seat tube, you also need to ensure that the top tube measurement along handlebar positioning also works for your body type.

The more hunched over you are over the bike, the more aerodynamic you are. For casual riders, a less aggressive angle will result in less strain on the lower bike during the long rides.

Mountain Bikes

For road bike riders looking at MTBs, sizing can be a bit confusing because MTBs tend to have a smaller seat tube and longer top tube length than their road bike cousins. For a comparison, have a look at the diagram below.

MTB seating positions are less aggressive than road bikes. You need to be able to look forward to avoid obstacles and dangers!

The vast array of MTB styles means that the general sizing that manufacturers use (small, medium and large) is ideal. As I mentioned earlier, with MTBs, the sizing quoted is generally quite a good guide on which size bike you’ll end up buying.

Hybrid Bikes

As I mentioned earlier, I think of hybrid bikes as a road bike with flat bars. They are a bit bulkier compared to a road bike, so this allows them to perform well on light off-road trails. These bikes also have the versatility to maintain great performance and speed on regular roads.

Hybrids are great for commuting and should be enough to enjoy a bit of off-roading on weekend rides!

Like all bikes, hybrids are generally measured by frame size. As highlighted above, the sizing of hybrid bikes is comparable to the sizing of mountain bikes.

Other Important Factors To Consider

Invest In A Bike Size Fitting

Depending on how much you’re getting into cycling, I personally think paying for a professional bike fitting is entirely worth it. From personal experience, it made a huge difference in my power output and really reduced the stress on my lower back and knees.

Fitting specialists will take all your body measurements and help walk you through the process of fine tuning the bike setup specifically for your body and current capabilities. It will generally involve you jumping on a bike and then they record / analyse how you ride, making small adjustments, test, and repeat.

Try Before You Buy

At the end of the day, finding a well fitting bike is like finding any well fitting piece of clothing – you will only know once you try it on. Seeing a bike in person, trying it out, and getting a feel for it is often the best way to know if it’s right for you.

A few body measurements will help point you in the right direction. It will even help rule out the easily identifiable ‘too big’ or ‘too small’ bikes when shopping online. But, nothing will truly confirm that a bike is the right one for you until you take it for a spin.

Many bicycle brands and bike shops offer demo days or demo events to allow customers to test ride bikes. This is also a great opportunity to ask questions and speak to knowledgeable staff members.

Listen To Your Body

The above information should provide you the basic outline next time you’re shopping for a bike online. However, this is somewhat of an art and not an exact science!

It’s all about experimenting with what feels right and comfortable given where you’re at with your personal health and fitness.  Of course this can change over time as you improve and you can alter your riding style accordingly at that time.

If at any point you’re feeling pain, numbness or a tingly sensation, it’ll likely indicate a poor bike fit. You stop riding that bike until you resolve any issues.  Issues can range from anything like neck pain, back pain, elbow pain or knee pain. I would suggest heading to a local bike shop or physiotherapist to help with any bike fitting problems.

Bike Size Summary

For cycling pros riding the Tour De France, there’s meticulous analysis that goes into sizing a bike for their body type. But, for us mere mortals, we can just take the above into consideration when we’re buying a bike. 🙂

In all seriousness, with the information in this article, the help of a knowledgeable bike sales personnel and with a bit of trialling of bikes on your part, you should be able to find the perfect bike for your particular needs!

Need some ideas on which bike to buy? You can check out a few of our bike round ups here:

Hi, I'm Harry, the owner of this site! A 30-something MAMIL - a middle-aged man in lycra. An avid cyclist who is looking to maintain a baseline level of fitness to be able to enjoy the great outdoors on weekend rides with his mates!

Leave a Comment