Choosing the Right Bike Size – A Comprehensive Guide

Bike sizing is a minefield.

Seat tube lengths and recommended bike heights are not always reliable because different bikes have different fits.

And this usually leads to most cyclists getting a bike without a formal fitting.

While it’s not the worst thing in the world, the truth is a wrong bike fit has some serious ramifications.

It includes hurting knees, back, and hands. It also impedes your riding performance and makes your experience uncomfortable.

In my opinion, anything along those lines calls for an immediate adjustment to your bike size.

But how do you go about it?

You could start by getting advice from your local bike shop on what size of bike to buy.

Or you could proceed to read our guide that outlines everything you need to know about the right bike size for you.

Figuring Out the Right Bike Size

There’re three main ways to determine the right bike size for you.

And in the section, we’ll look at each of the methods in detail.

1) Method One: Bike Size by Height

The first step in determining the ideal bike size is considering the frame size.

It’s by far the easiest way to check whether a bike is fit for you or not.

The frame size usually refers to a bike seat tube, measured from the center of the crank to the topmost section of the head tube or whether the seat is positioned.

To determine whether a bike is right for you, simply take your height and divide it by the top tube length.

The formula is the rider’s height/bike or frame size.

This simple formula is also known as the bike size chart by height or bike frame bike size chart.

Of course, it’s not definitive and may vary because it doesn’t consider the inseam length and varies depending on the manufacturer’s specific standards.

However, it’s a conventional and somehow arbitrary way to determine the idealness of a bike size. And this is because some heights tend to compliment certain bike frames.

What’s more? With the correct bike size frame, it’s easy to adjust other bike components such as handles and saddle height.

So, it’s easy to customize your bike size and riding experience if you’ve the frame size correctly matched.

Here’s a breakdown of the common rider heights and their corresponding bike frame sizes;

1)      4′-5′ rider height corresponds to a 13-14″ frame size

2)      5′-6′ rider height corresponds to a 15-16″ frame size

3)      6+’ rider height corresponds to 21+” frame size

But I reiterate that while frame size is one of the simplest ways to determine the right bike size, it’s not definitive and won’t offer a perfect fit.

Instead, it’s only a decent way to provide a general guide on whether your bike frame will be short or tall.

Frame sizing is usually different between brands.

2) Method Two: Calculating Your Bike Size

My second method of finding the right bike size is more involving but with far much more precision than the first method.

The formula for the second method is Bike Type x Leg inseam = right bike frame.

One of the critical elements of this formula is determining the type of bike. Different bike categories have different multiplier values (saddle tube lengths).

The common multiplier values for each bike categories are:

1. a)       Road bikes- x 0.70
2. b)      MTBs- x 0.685 
3. c)       City bikes- x 0.685 

Here’re the exact steps to follow when determining the right bike size for you.”

Determine leg inseam

Inseam is the length or distance from your crotch area to the ground.

So, start by taking off your shoes, and then simply stand at least 6 inches feet apart.

Then, measure the inseam length, starting from the ground, all the way to the crotch area on the inside leg, preferably where both legs meet the waist.

The inseam should represent the distance from the ground to where your bike saddle should be positioned.

Consider your bicycle type

As mentioned a little bit earlier, each bike category has different multiplier values (seat tube length).

Determine the ideal frame size

The final step is to calculate the ideal frame size using the values above.

Here’s a formula guideline to use for the different bike categories:

•         Roadie bike: 0.70 multiplied your leg inseam= ideal frame length
•         MTB: 0.685 x your leg inseam= ideal bike frame size
•         City bike: 0.685 x your leg inseam= ideal bike frame size

Here’s a practical example of finding the ideal bike frame size based on the inseam height.

If you’ve an inseam height of 65cm and looking for a road bike, the right road bike size frame should be:

65 x 0.70= 45.5 cm

Your ideal roadie should have a 45.5 cm bike frame.

Here’s another example.

If you’ve an inseam height of 76cm and looking for a mountain bike, the ideal mountain bike size frame should be:

76 x 0.685 = 52.06

So, the ideal and right-fitting mountain bike frame size should be 52 cm.

3) Method three: Bike Size Chart

The other method is using the available bike size charts.

It’s one of my favorite methods of determining the ideal bike size for me.

Of course, the charts also depend on the type of bike category. For example, a road bike size chart is vastly different from a mountain bike size chart.

The good news is we’ll break down some of the popular bike categories and their corresponding bike size frame sizes.

Road Bike Size Chart

There’re two main ways of sizing a road bike, and they include:

1)      Saddle tube dimension

2)      Top tube

The seat tune is usually the distance between the saddle and the bracket measured in centimeters.

Usually, the range for the seat tune starts from 46 cm to 64 cm.

On the other hand, the top tube refers to the horizontal distance between the saddle’s center and the frame.

Usually, the saddle tube is used to determine the road bike frame and the stem length and reach of the handlebars.

Combined, these measurements will determine your overall riding posture, specifically whether you’ll be riding upright or hunched.

For example, if your bike has a longer steam reach, you’ll take on a hunched and more aerodynamic riding position.

Conversely, if you’ve a shorter stem reach, you’ll take a more upright stance.

Here’s a general road bike size chart outline of the three popular road bike size and their corresponding height measurements;

•         Small frame size (S)- 5’4” to 5’7”
•         Large frame size (L)-5’10” to 6’0”
•         Extra large frame size (XL)- 6’0” to 6’3”

Mountain Bike Size Chart

Sizing a mountain bike is different from a road bike.

First, it depends on the MTB’s age.

See, before 2000, most bikes came with an A-frame, but the mountain bikes had smaller wheel sizes and a higher bottom bracket.

However, the pre-2000 bikes had longer crank arms for navigating the steep hills and greater sideway controls.

All of that changed after the 2000s when new technology set off.

Either way, whatever mountain bike option you’ve, ensure it’s comfortable and optimizes your cycling performance.

Also, remember mountain bike geometry is less aggressive than a road bike. It keeps the riders upright to give them greater control when navigating the challenging trails.

Mountain Bike Size Chart: Critical Things to Keep in Mind

As we mentioned earlier, sizing a mountain bike is different from sizing traditional bikes.

Remember, mountain biking involves riding on challenging and gnarly terrains, so you want something that rides differently and with nice control.

The ideal mountain bike fit should allow your feet to reach the bottom of the stroke when pedaling and experience a slight leg bend.

You also need to think out of the box when purchasing mountain bikes for women. Women have narrower shoulders and long legs.

Consider purchasing the women-specific mountain bikes with shorter frames and narrower handlebars.

Mountain bike sizing for your kid is also a different concept.

The ideal stand-over height for a kids mountain bike should provide two to four inches of clearance.

When sitting, they should take an upright position when holding the handlebars, and when pedaling, their legs should be slightly bent at the bottom pedal stroke.

Hybrid Bike Size Chart

Hybrids are a combo of road and mountain bikes.

When sizing a hybrid bike, ensure a one-inch clearance between the top of your bike and the crotch area.

Kids Bike Size Chart

Kids bikes don’t use the conventional frame method used in adult bike sizing.

Instead, they use the wheel diameter size.

Here’s a breakdown of the inseam height and the corresponding bike wheel size for a typical child’s bike.

12-17” inseam goes with 12” wheels

18-22” inseam goes with 16” wheels

22-25” inseam goes with 20” wheels

Nonetheless, most of the kids bikes are highly adjustable and will accommodate their growth spurts. However, it’s still a good idea to consider their perfect bike sizing.

What to Keep in Mind When Selecting the Ideal Bike Size Guide

The right bike size is more than just the three methods we’ve listed above.

There’re a couple of other crucial factors to consider when determining the right bike sizing guide.

The most critical considerations include:

Height & Inseam

It’s easy to assume that riders of a similar height can fit on the same bike, but that’s far from the truth.

We all have unique bodies, and having the same height doesn’t necessarily guarantee that we can use the same bike.

For example, I’m a big and tall 6’5″ guy, but with an inseam of 32″. On the other hand, my buddy Jake is also the same height but with a shorter torso with long legs. He has an inseam of 36″.

Therefore, while we’ve a similar height and can ride a similar bike, it’s technically impossible to find the right bike size to comfortably accommodate both of us.

Frame

Even with proper bike sizing, you also need to consider the frame size. A wrong size bike frame will make pedaling an uncomfortable experience.

For example, if your frame is too short, your legs will feel crumpled and won’t fully extend to their potential for maximum cycling power.

On the other hand, if the frame is too long, it won’t allow you to attain a full leg rotation for pedaling at higher speeds.

The ideal way to determine the right frame size is using the stand-over test.

Keep the bike upright, and straddle to the frame tube with your feet shoulder apart. Close into the bike, with the pelvic bone flush to the frame.

If the frame size is right for you, it should have an inch difference between the frame and your crotch.

However, this will only work for hybrid, road, racing, and touring bikes.

Mountain Bike Frame & Kids Bikes Frame

Both mountain bikes and kids bike frames have different sizing parameters.

Determining the idealness of a mountain bike frame uses a similar process to that of a road bike, but the only difference is the distance between the crotch and frame.

It should be 2 inches instead of one inch.

When it comes to sizing a kid’s frame, you need to have them sit on the saddle while the balls of their feet touch the ground.

Saddle Position and Height

Saddle height is crucial for comfort and performance.

There’s no ideal seat position because all cyclists are different and have different body frames. It’s a personal preference.

However, if the saddle is too low, it’ll take much of your pedaling power and inhibit proper leg extension. In my mountain bike racing, I notice that I lose 20-25% of my power in my feet when my saddle is low.

On the other hand, if the bike’s saddle is too high, you’ll struggle to get enough cadence to keep rolling and stretch a lot.

Simply put, choosing the wrong saddle height will compromise your riding experience and impede your performance.

The ideal saddle position should be comfortable and help to optimize your cycling.

Any easy way to fix an ideal saddle position is by ensuring the seat is positioned so that your feet rest on the pedal. And when extended, your feet should be in contact with the ground.

While at it, ensure that your shoulders don’t have to sway sideways for you to make contact with the ground. 

Handlebar Position

The handlebar position is also critical in the overall comfort and bike riding experience.

An incorrectly positioned handlebar causes more discomfort and pain, especially on the wrist, shoulder, and back. It may also lead to hand soreness.

Now, the ideal handlebar position will also depend on the bike category.

For example, road bikes have an aerodynamic geometry, so the handlebar is slightly lower than the saddle to accommodate the “bend” position.

Touring bikes and cruisers have wider handlebars, the width of your shoulders.

The mountain bikes have the handlebars positioned slightly below the addle for more control when navigating challenging terrains.

Finally, hybrid bikes come with a high seat to accommodate the upright riding posture.

Of course, none of these handlebar positions are cast on a stone. Most bikes can adjust the handlebar to suit your riding style and body type.

Wheel Size

Wheel size is the diameter of a wheel and is usually indicated on the sidewall.

The wheel size depends on the use of the bikes. For example, mountain bikes generally have larger 26″ or 29″ wheels for more surface contact and increased traction.

On the other hand, road bikes have skinnier wheels and tires for more aerodynamic performance ad less drag.

Wheel size for kids bikes are usually much smaller but will differ depending on their age. For example, ages 3 to 5 have 12″ wheels, 16″ for 5 to 7, etc.

Choosing the Right Frame for your Bike

When considering the right bike size, you must pay attention to the bike frame.

Your entire bike is built around the frame. However, unlike handlebars, or saddles, the frame isn’t adjustable, so you must get them right on your first purchase.

Generally, bike frames are all-metal, or carbon made.

The shape also differs depending on the type of bike category. Ad in most cases, the frame configuration determines the function of a bike.

Some of the popular bike frame configurations include:

Road bikes

Road bikes are often used by commuters or fitness racing.

The road biking frames are large and triangular-shaped. They’re also usually parallel to the ground.

Mountain Bikes

MTB has a lower COG to promote better handling and control, especially in challenging terrains.

Therefore, their frames are more compact, and sometimes, they slope slightly away from the handlebars.

The MTB also has wider tires for more ground contact.

Hybrid Bikes

A hybrid combines the structural and design properties of a road and mountain bike.

Their frames are measured in centimeters and have the properties of both bikes.

Cruiser Bikes

Cruiser bikes, popularly referred to as beach cruisers, are mainly used for comfort riding.

They’ve wide handlebars and sideways S-shaped or curve frames.

The s-shape frames let you sit upright when cruising around.

Kids Bikes

The kids bikes have smaller frames, resembling those of mountain bikes. It helps to keep the kid in control.

Always Try Before Buying

Even with bike sizing and everything, you must always try your bike first.

I know it’s an overused and cliché advice, but trying the bike in person and feeling it is the best way to know whether a size bicycle is right for you.

The good news is that many local bike shops and bike manufacturers usually have in-shop or demo events that allow riders to test and determine whether a bike fits their needs.

Listening to your Body

Knowing the right bike size will make bike selection easier right from the beginning.

However, there’re a couple of other ways to use to determine whether your setup is right or not.

For example, if you start experiencing body pain, elbow pain, discomfort, numbness, and a general unpleasant feel, you need to understand the size bike isn’t the right fit for your needs.

Bike Sizing Guide Frequently Asked Questions (FAQs)

Q: What if I fall between two frame sizes?

A: If you’re between two sizes, pick one of two sizes if they’re adjustable. However, if you’ve shorter arms and smaller stature, pick the smaller option for a comfortable ride.

Q: Is the correct bike fit important?

A: Yes, the right bike fit is crucial for several reasons.

One, it promotes a comfortable riding experience. It saves you from an unpleasant ride experience and makes you enjoy your ride even more.

Secondly, it ensures you’re not hurt. See, an ill-fitting size bike usually results in numbness and hurting on your knees, arms, elbows, and legs.

Finally, the best fitting bike gives you more control and power and allows you to pedal smoothly.

Q: Do women and kids need a bike size chart?

A: Yes, women and kids will equally benefit from a bike size chart.

Following the guidelines of a bike size chart ensures all riders enjoy a comfortable riding experience and that they pick a bike suited for their body type.

Q: What if my bike is wrongly-sized?

A: If you discovered your new bike has a wrong fit, you could request a replacement from your merchant.

But if it’s impossible, there’re a couple of things to do to fix the size issue.

•         Adjust the bike’s seat height, either to the front or rear
•         Consider a longer or shorter stem
•         Consider a longer or shorter seat post

Finally, give yourself time, and you should start to feel right.

Wrap Up

Biking sizing is as important as the bike itself.

Having the right size bike is necessary for a comfortable and pain-free ride.

And the good news is I’ve shared a couple of ways and different bike size charts to ensure you’ve the right bike size for your cycling needs.

Whether you’re trying to fit a road bike, a touring bike, or a mountain bike, our size charts above will help you find the correct size bike fit and everything. You won’t even need to go for professional bike fitting services.

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