The Definitive Guide to Bike Size
Remember the old-fashioned method of determining the right size of bike for your needs? If your toes could just touch the ground while you were sitting in the saddle of the bike, then you were good. Except if you needed to stop quickly. Then you had to learn how to put the frame of the bike to one side so your entire foot could hit the ground.
Did that happen with you growing up? How many times did you end up crashing your bike because you couldn’t get your feet down fast enough?
That is evidence that you didn’t actually have the right size of bike. Now you’ll find plenty of charts, graphics, and advice offered online if you’re looking for a definitive guide to bike size. All of that data is pretty good, but it is generic in nature.
Sizing a bike is a very personal experience. There are no shortcuts. Finding the right size for a mountain bike is not the same process as finding the right size for an incumbent bike. So if you’re ready to find a great bike that you plan to ride every day and you’re concerned about the size of its frame, seating position, and other features, then it’s time you took the personalized approach.
What Size of Bike Do I Need?
The size measurements that you’ll find published for the average bicycle are based on the frame used for its design. The goal is to find a bike that doesn’t make it uncomfortable or difficult to actually ride it. If the frame is too large, then you won’t receive a full drive from your leg rotation. If it’s too small, then your knees might just bash you in the nose if you hit the right bump somewhere.
The easiest way to determine what size of bike you need is to measure your inseam. Then compare this measurement to the upper frame measurement that has been published in the best bike reviews. If the inseam is just a little larger than the bike frame, then you’ve probably found the right size of bike to try on.
You can confirm this by stepping over the cross bar of the frame. If both feet can stand there flat on the ground and you still have easy access to the seat, then you’ve got the right size of bike. If not, then see if you can adjust the height of the saddle to accommodate your needs. If you still cannot sit properly and be able to easily put your feet on the ground, then you’ll need to go down a frame size.
What You Need to Know About Bike Sizing
There can be a lot of confusion when shopping for a bike that’s the right size. The primary issue is the fact that there are two different sets of sizing systems that are utilized by our industry today. If you use the wrong one, you’re going to find the bike size is very off.
What are the two bike sizing systems?
- Frame measurement.
- Wheel diameter.
When looking for the right size of bike, you’ll find that road bikes use frame measurements to indicate size. Many road bikes offer size measurements in centimeters. Hybrid bikes will also use frame measurements as their primary sizing option, but most manufacturers describe them in inches instead.
Then there are the mountain bikes. It’s a free-for-all with this type of bike. Not only will you find mountain bike frames described in inches, but you’ll see them in centimeters too. You’ll also find them described by wheel diameter only. Some hybrids and mountain bikes are even given a standard sizing option only, like S, M, or L.
Should you be purchasing a “medium” mountain bike? Maybe you’re shorter and think that an “XS” mountain bike might be the best option?
So here’s the key to making sure you get the right bike size. If you see a 26-inch bike, that’s probably the wheel diameter of the bike. That’s not a reflection of the actual frame. Go deeper into the product description or the bike review to see what the actual frame dimensions happen to be.
Other standard wheel dimensions are 27.5 inches and 29 inches. The 29-inch wheel diameter might also cause the bike to be referred to as a “29er.”
How to Measure Bike Size Properly
To figure out what bicycle size is the proper one for you, it will be necessary to take a few measurements.
- Your arm length. Measure from the end of your collarbone to the middle of your fist. Make a closed fist and hold your forearm upward for the most accurate measurement.
- Your torso length. This is the measurement from the groin to the sternum. There’s a V-shaped curve to your neck where the collarbone dips down. That’s the measurement point you’ll want to use.
- Your leg inseam. This is the measurement which is typically your ankle to your groin. For bike measurements, you’ll need to go all the way down to the back of your heel for an accurate measurement.
These are then the measurements you can use for the sizing charts that are published for many makes and models of bicycles today. Most manufacturers use what is called a “stand-over height” for the size of the bike. If your inseam measurement is 1-2 inches more than the stand-over height, then the bike should work for you.
Please note: Some mountain bikes may require up to 4 inches in clearance when comparing the inseam measurement to the stand-over height. The manufacturer will note the difference in the documentation and bike reviews for your preferred model. If they do not, then assume a minimum clearance of 2 inches will be required for a mountain bike.
If you’re not sure about the accuracy of the stand-over height measurement, you can also determine the right size of a bike by determining the top tube length and comparing that to your other measurements. It’s a simple formula to help you determine if you’ve found the right bike size.
Add your torso length to your arm length. Then divide that combined measurement in half.
What Is the Best Bike Size for My Height?
Height is actually the least accurate measurement to consider if you’re shopping for a brand new bike. This is because everyone has been created a little bit differently from one another. Someone who is 5’7” might have longer legs and a shorter torso than their neighbor. If you just went off of a sizing chart, then the suggested frame size would likely be 54-55 centimeters.
This is why taking your inseam measurement is a better solution to finding the right size of bike. Although two people of the same height may have similar measurements, it only takes a fraction of an inch in differences to alter the proper frame size that should be utilized by that rider.
Then there’s the style of bike that should be considered in the size consideration as well. There are four very different frame types that are common in our industry today. Each one has unique components to it that must be considered for height purposes.
- Road bikes. This bicycle frame creates a standard triangle from pedals to saddle to bars. This means the stand-over height measurement must be carefully considered because of the height of the upper cross bar in the frame.
- Mountain bikes.This bicycle frame makes the same triangle design, but the upper bar is put at a dipped angle compared to the road bike. This reduces the stand-over requirement, but does not change the saddle measurement or top tube length considerations that must be made.
- BMX bikes.This bicycle frame is designed for general racing, stunt, and freestyle riding needs. For this reason, height is usually not a consideration. If anything, you just need to make sure that the bike isn’t built too low to the ground for your personal preferences.
- Kid’s bikes.This separate category of bicycle has frames that are 24 inches in size or lower. To meet the needs of each child, you’ll find several generic sizing categories in the 12-18 inch range quite often. Look for models that offer adjustable saddle height options to maximize the value of this investment.
There are many sites that will offer you a “bike size calculator” to help you determine what your best bike height will be. Many of these are based on height and weight only and do not take the other measurements discussed into account. This creates the potential of purchasing a bike that is too big or too small to meet your needs.
Shortcuts in our industry are few and far between. Trust yourself to take your measurements and your riding experience is going to be better for it.
How to Size a Mountain Bike Properly
Mountain bikes can be one of the most versatile frames that you own. They can also be one of the most difficult to determine proper sizing. You’ll want to follow these steps to make sure that you’ve sized your mountain bike in a proper fashion.
Step #1: Measure with your shoes. Some sites tell you to take your shoes off for your height measurement. Let’s be serious for a minute: are you really going to ride your mountain bike without shoes? Of course not. Leave them on. If you prefer to ride with boots, then take your measurement with them instead. This will help you be able to find an accurate frame size for your needs.
Step #2: Determine the type of mountain bike that you want. Although all mountain bikes are pretty similar, there are some key differences. Cross-country bikes tend to be a little taller and firmer in their ride. Trail bikes tend to be a little smaller and a bit longer. Hybrids are a mix of the two, depending on the manufacturer. Wheel-size requirements also play a role. In general terms, if you want an off-road bike, you’ll need one that is as tall as possible, but still be comfortable for you to ride.
Step #3: Get the saddle right. In terms of measuring a mountain bike for a solid fit, it’s better to have a smaller frame with an adjustable saddle than it is to have a frame that is too large. You want to have a nice bend to your leg rotation on the pedals because this will give you more control over your speed. Go too low on a mountain bike and you lose that control, but go too high and you lose your center of balance.
Step #4: Understand wheel size and how it relates to bike size. Buying a 29er as a mountain bike is a very different experience compared to purchasing a cross-country mountain bike. With a standard 26-inch wheel, the 29er automatically has 3 additional inches of height that must be factored into your sizing calculation.
If you’re thinking about purchasing a 29er, then there must be a certain level of adjustment that goes into the riding experience. Out of all the bikes that are on the market today, it is the 29er mountain bike that feels most like a tank. It will be difficult to ride on trails when you first starting using it.
This isn’t a size issue. This is a “heft” issue. You’re just not used to having such a massive bike to navigate.
Over time, this feeling should go away. Many 29er users even talk about how it is hard for them to go back to the smaller standard size at 26-inches because the bike feels so light and small compared to their usual ride.
How to Choose a Mountain Bike That’s Right for Me
Choosing the best mountain bike means approaching this question in a specific way. Here are the three points of consideration that should be taken into account whenever looking at a new bike.
- Your mountain bike should fit you well. Compare your personal measurements to the measurements of the bike. If you’ve got 2-4 inches of clearance on each measurement, then you’ve got a bike that will fit you well. Anything smaller may create discomfort and anything larger means you’ve got a bike that’s potentially too small.
- The key features of a mountain bike include the wheel size, the materials of the frame, its suspension, and its gearing. Some manufacturers would also include the design of the braking mechanisms as a feature, though most mountain bikes usually have disc brakes.
- Your riding style will dictate the type of mountain bike you should own.
If you’re looking for more specific information regarding the sizing of a mountain bike, REI offers you a comprehensive look at the various types of mountain bikes that are available and what sizes may be appropriate to meet your needs.
What Size of Hybrid Bike Do I Need?
Sizing a hybrid bike is a lot like sizing a mountain bike. You’ll need to consider your height and your inseam length to then compare it to a bike frame size that works best for you. The inseam measurement is the most important out of the two, so you can guesstimate your height if you wish.
Hybrid bikes are usually measured by their frame size in inches. This is the distance from the crank to the top of the frame, which is usually at the seat tube. If you’ve already measured yourself out for a mountain bike, then your measurements will work for a hybrid – just subtract about 2 inches and you’ll find the best option for your needs.
Although a customized fit will always be your best option when shopping for the best hybrid bikes, you may not always have that luxury. For that reason, you may wish to find the right size for your hybrid bike with this helpful sizing guide.
How to Choose the Best Commuter or Cruiser Bike Size
Commuter bikes, cruiser bikes, and city bikes are all a little different from the other types of bicycles that are available today. These bikes feature frames that are designed to be a one-size-fits-all solution for riders. This makes them a suitable choice for most cycling enthusiasts of any height or body type.
This is because of their step-through design. The frame on these bikes doesn’t feature the same top crossbar in the frame as mountain and men’s racing bikes typically feature. This eliminates the standover measurement in many instances because even a 4-year-old can feasibly stand over most of the bikes that fit into this category.
This means the most important measurement comparison for commuters, cruisers, and city bikes is the height to seat post. Some might say the diameter of the seat post is important, but it really is not. Only certain post diameters are going to work with the bike frame. This only becomes a measurement concern if you intend to replace the saddle and seat post after purchasing the bike.
So you’re going to want to look for two specific points of reference in the best bike reviews and bicycle descriptions.
- The minimum insertion measurement.
- The maximum insertion measurement.
These are the two lines on the seat post where the bike can be safely used. There may be additional room on the post to change the height outside of these measurements, but using a bike in such a way is likely to void its warranty.
Once you’ve determined the two insert measurements, you’ll want to have someone measure from the top of your hip down to the sole of your foot. When you’re sitting in the saddle, you need to have a full extension of your leg to maximize the strength of each pedal stroke. It also helps to maintain your rhythm.
If a bike is too small, then your legs will splay out as you pedal and it’s going to be an uncomfortable experience commuting to work or exploring the city. If a bike is too large, then you’ll struggle to maintain any semblance of consistent speed while riding your bike.
These issues are enhanced in this particular frame-style category because many commuter bikes and city bikes are single-speed.
You’ll want your physical measurement to be within the range of the minimum/maximum insertion measurements for the seat post. As long as it fits, you’ll be able to fit on that bike. If not, then you’ll need to find a different frame to meet your needs.
What Size of BMX Bike Do I Need?
Sizing a BMX bike is a little different than other bikes. This is because a standard top-tube BMX design is going to be 20 inches. It’s up to you to make sure that you can fit on that bike in a comfortable way.
If you’re looking at professional BMX bikes, or at least non-standard models, then you have some additional size options for your bike frame. There are 8 different sizes that are available across all BMX makes and models today. Which of these would work best for you?
- Micro Frame. Offers a top tube length of up to 16.5 inches, a stem length of up to 35 millimeters, and a crank length of up to 155 millimeters. Rated for riders who are 52 inches in height or lower.
- Mini Frame. Offers a top tube length of up to 17.5 inches, a stem length of up to 40 millimeters, and a crank length of up to 165 millimeters. Rated for riders who are between 50-58 inches in height.
- Junior Frame. Offers a top tube length of up to 18.5 inches, a stem length of up to 45 millimeters, and a crank length of up to 175 millimeters. Rated for riders who are between 54-61 inches in height.
- Expert Frame. Offers a top tube length of up to 19.5 inches, a stem length of up to 48 millimeters, and a crank length of up to 175 millimeters. Rated for riders who are between 60-64 inches in height.
- Expert XL Frame. Offers a top tube length of up to 20 inches, a stem length of up to 48 millimeters, and a crank length of up to 175 millimeters. Rated for riders who are between 62-66 inches in height.
- Pro Frame. Offers a top tube length of up to 20.5 inches, a stem length of up to 55 millimeters, and a crank length of up to 180 millimeters. Rated for riders who are between 63-68 inches in height.
- Pro XL Frame. Offers a top tube length of up to 21.25 inches, a stem length of up to 55 millimeters, and a crank length of up to 190 millimeters. Rated for riders who are between 67-72 inches in height.
- Pro XXL Frame. Offers a top tube length of up to 22 inches, a stem length of up to 60 millimeters, and a crank length of up to 190 millimeters. Rated for riders who are over 72 inches in height.
Ultimately, the sizing of a BMX bike is more about being comfortable than it is finding a specific frame. It also depends on the type of work you plan on doing with your new bike. You may find that a slightly smaller BMX works better for stunt work, while a slightly larger frame works best for flatland riding.
How to Choose the Right Size of Fixie
If a fixed-gear bike is more your style, the process of finding the right bike size is pretty similar to road and mountain bikes. You’ll need to consider the various frame components and their dimensions, then compare those measurements to your height. With fixies, you also have the additional challenge of maintaining foot contact with the pedals, so you generally want to give yourself a couple inches of clearance instead of sticking to the minimum/maximum height guidelines.
Each manufacturer also has their own height recommendations when it comes to their bikes. For this guide, consider the following as generalized recommendations for height instead of a comprehensive list.
- For riders under 67 inches in height, a 52-centimeter fixie frame is recommended. This generally means that you’ll have a top tube that is 52-54cm in length. The seat tube will be a couple of centimeters shorter than the top tube. The head tube should be 80-90cm in size and the fork offset should be right around 70cm.
- For riders under 73 inches in height, a 55-centimeter fixie frame is recommended. This will usually give the rider a bike that has a top tube of about 55-60cm in length. The seat tube will be about the same size as the tope tube. You’ll find a shorter head tube and seat tube angle on the larger bike, but the head tube length should be over 100cm. The fork offset may be just a little larger on a 55cm fixie than a 52cm fixie.
- For riders 74 inches in height or above, a 59-centimeter fixie frame is recommended. This fixie will have a 59-65cm top tube and seat tube. The heat tube angle is the same as a 55cm fixie, but the seat tube angle should be slightly more. The head tube should be approximately 140cm, with the fork offset near 75cm.
If you are shorter than 5’3”, then you may wish to look at smaller fixies to see if their frame requirements match your height requirements with more specificity. Some manufacturers produce fixies that are 48-50cm in size, giving you a more comfortable riding option than trying to force yourself onto a larger bike.
Not every manufacturer makes smaller fixies. You may also need to look at kid fixies if you’re struggling to find a 52cm fixie frame that works for you.
How to Choose the Right Size of Electric Bike
If you’re in the market for an electric bike, then your sizing requirements are fewer than most other bikes. This is especially true for those who have no plans to use a feature like pedal assist. Yet a correctly sized e-bike will still give you better balance and stability than one that is larger or smaller than what is recommended for your physical height.
Almost all electric bike frames are sized from the bottom bracket center to the top of the seat tube. That’s basically where the pedals are cranked to the place where your seat slides into the bike.
Then you’ll want to take these three additional sizing issues into account to make sure your e-bike meets your needs.
- Watch out for standardized sizing. Many electric bikes are sized as “small,” “medium,” or “large.” Small frames are generally for people up to 70 inches in height. Medium frames support individuals who are up to 76 inches in height. Large frames would be for anyone over 72 inches in height.
- Know the clearance measurement. In the world of e-bikes, the clearance measurement is what other bike types would consider the standover measurement.
- Understand gender specific sizing. Because of the speeds that e-bikes can achieve, manufacturers have created female-specific bikes with lower and shorter top tubes. They also typically have narrow grips and a wider saddle.
Then, like most other bikes, you simply need to compare your physical requirements to the frame measurements. Choose the electric bike that best fits you.
What Size of Bike Is Right for My Child?
Kids’ bikes are generally sized in the same way as an adult bike, but only wheel diameter is usually offered in the bike’s description. If you’re purchasing a 14-inch standard kids’ bike, then you’re purchasing a bicycle which has wheels that are 14 inches in diameter. For youth and young adults, a standard bicycle size would be 20 inches.
Toddlers will typically have bikes that are either 12 inches or 14 inches in size. Intermediate riders, such as a child who is still using a bike with training wheels, will use bicycles that are 16 inches or 18 inches in size.
Some tricycles may also be included in this bike category. Their measurements are also different. Most tricycles for kids are designed as a “big wheel” bike. This means the front wheel of the tricycle is much larger than the back wheels. The description of the tricycle will give you the diameter of the larger wheel.
Occasionally, there may be 24-inch bicycles marketed as a kids’ bike as well, usually in the mountain bike market. That’s the maximum size for a kids’ bike. Once you reach 26 inches in wheel diameter, you’ve entered the world of the adult bike.
Now that you know what sizes are available for children, it’s time to make sure you purchase the correct size for their physical shape. Training wheels or balance bikes can be used on any kids’ bike. It is important to purchase the correct frame size for learning instead of relying on purchasing a “beginner” bike for children.
It’s easy to measure a child for a bike. Here are the steps that you’re going to want to follow.
- Take their shoes off. Then have the child stand with their back against the wall. Their feet should be about a shoulder-width apart.
- Have them hold a book between their legs. It shouldn’t be a heavy book. Just one that will help you make sure that their leg placement remains consistent while you are taking an accurate measurement. You may need to have a friend or sibling hold the book in place.
- Measure from the floor to the spine of the book. The spine of the book is acting as the top of the bike frame for this measurement. Take a measuring tape or yardstick, measure from the floor to the top of the book spine, and note the measurement in both inches and centimeters.
Then you can quickly compare your measurements to the frame measurements that are offered by bicycle manufacturers. Because wheel size is used to market these bikes, you’ll want to look at the maximum seat size and frame size to make sure the bicycle will work on all surfaces for your child.
You can also use a helpful kids bike size calculator to confirm your results.
Are You Ready to Find the Right Bike Today?
Finding the right bicycle means finding one that accommodates your physical size and shape. The best bike in the world won’t do any good if it only supports 150 pounds and you weight 225. The same is true when it comes to the size of your bike when comparing it to your size. If you’re not comfortable on your bike, then you are increasing the risk of being injured should something unforeseen occur.
How to find the right bike size depends on the style of bike you want. It also depends on the frame-type you prefer. Some bicycles work for kids only. Others are perfect for men and women. Then you’ll find gender-specific bicycle measurements that may need to be followed as well.
When you follow the sizing process, you’re more likely to purchase the best possible bike for your needs the first time around. Use the tips found here to take your own measurements, compare that data to what the bike frame dimensions happen to be, and you’ll be able to explore more roads and mountains in comfort starting today.