Bike Size Guide and Charts

 

What Size Bike Do I Need?

Regardless of the type of bike you want, care has to be taken to ensure that you get the correct size and fit for your body. This is important, not just from for the comfort factor, but also from a safety perspective. Having a grasp of how to fit yourself to a bike is especially important when ordering online.

How to Measure a Bike?

To learn the right size bike for you, you need to understand the basic principles of bike measurement. In general, road bikes are measured in centimeters, while mountain bike measurements are displayed in inches. This is a long held manufacturing custom, and if you see the dimensions of a bike shown in inches, the chances are high that you are looking at a mountain bike, and road bike if it is in centimeters. Bikes are measured mainly by the length of the seat tube. This is the vertical tube beneath the seat which runs down to the point where the crankshafts and pedals are attached to the bike frame. The length is measured from the top point where the seat is attached, to the bottom bracket (BB) where the crank is bolted to the frame. The horizontal length of the frame (and the bike) is connected to the seat tube length. Bikes with taller seat tubes will have longer frames. Also keep in mind that different categories of bikes have their own frame geometry and size requirements. For instance, riding on mountain bikes on uneven terrain will require some aggressive riding on your part. So you might be better off with a bike that is one size smaller than what you would use on a road bike.

 

What is Stand Over Height?

The standover height is measured from the top of the top tube to the ground and use the same measuring conventions used for road bikes and mountain bikes. This is one of the most critical dimensions of a bike frame that you need to take into consideration when looking for the right bike size. The top tube on a bike is the horizontal tube in the top part of the frame, the one that runs from the top tube (which houses the handles in the front) to the seat tube in the back. On road bikes, the top tube runs parallel to the ground, while in mountain bikes and BMX bikes it often slopes from the front to the seat tube.

What Measurements Do I Need?

Learning how to measure a bike is just half the job done. If you look at a bike sizing chart, you will see body measurements linked to bike frame sizes. You will need three different measurements of your body to find the perfect bike size for your body structure. They include:

  • Height: This one is pretty obvious. Most manufacturers have bike size charts that show the appropriate bike sizes for specific heights. But this alone cannot guarantee a perfect fit, so the next two measurements are recommended.
  • Inseam Length: Stand with your feet planted around 6 inches apart, like you would do when you straddle a bike. Measure the length from your crotch to the bottom of your feet. And do remember to factor in the length increase from shoes when you take this measurement. You are not going to ride your bike around barefoot, are you?! Now to get a rough estimate of the ideal seat tube length for road bikes, multiply your inseam length by 0.67 for road bikes, and 0.185 for mountain bikes. For obvious reasons of safety and health, you need a healthy level of clearance between your crotch and the top tube. For road bikes, the minimum recommended clearance is 2 inches (or 10cm), while for mountain bikes get some extra room by having at least 4-5 inches of clearance. This way, you can avoid serious injury to your crotch area when you have to brake hard and jump off the saddle!

 

 

Fat Bike Size Chart

Fat Bikes Size Charts

 

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Mountain Bike Size Chart

Also used for sizing beach cruiser, comfort, and other hybrid bikes.

Bike Size Size Rider Height Inseam
13-14″ X-Small 4’11”-5’3″ 27″
15-16″ Small 5’2″-5’7″ 27-29″
17-18″ Medium 5’6″-5’11” 29-31″
19-20″ Large 5’10”-6’2″ 31-33″
21-22″ X-Large 6’1″-6’4″ 33-35″
23-24″ XX-Large 6’3″+ 35″+

 

*Approximate sizing. Your final choice is up to personal preference.
Suggest minimum 2″ of crotch clearance from stand over height.

 

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Road Bike Size Charts

Also used for sizing fixies, commuter, and other city bikes.

Bike Size Size (cm) Rider Height Inseam (in)
45-47 (17.5-18.5″) X-Small 4’8″-4’11” <27″
48-50 (19-19.5″) Small 4’11”-5’3″ 27-28″
51-53 (20-21″) Medium 5’3″-5’7″ 28-30″
54-56 (21-22″) Large 5’7″-5’11” 30-32″
57-59 (22.5-23″) X-Large 5’11”-6’3″ 32-33″
60-62 (23.5-24.5″) XX-Large 6’3″-6’6″ 33″+

 

*Approximate sizing. Your final choice is up to personal preference.
Suggest minimum 2″ of crotch clearance from stand over height.

 

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BMX Bike Size Charts

BMX Sizing: 16-20″ Wheels

Rider Height TopTube Length Wheel Size
4’4″ and under 15-16.5″ 16″/18″
4’2″-4’10” 16-17.5″ 16″/18″
4’6″-5’1″ 17-18.5″ 18″/20″
5′-5’4″ 18.5-20.5″ 20″
5’2″-5’6″ 19.25-21.5″ 20″
5’3″-5’8″ 20-21.5″ 20″
5’7″ and up 20.5″-22″ 20″

 

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Big BMX Size Chart

Over 20″ Wheels

Rider Height TopTube Length Wheel Size
5’2″ + 21-23.5″ 24″
5’4″ + 21-24.5″ 26″
5’5″ + 21.5-25″ 29″

 

 

How to Position Your Bike Seat 

Once you buy the perfect bike with the best frame size for you, it’s time to set the seat height. Getting the correct height is crucial to avoiding injury and getting the most out of the bike. There are many formulae and methods used by the professionals, like the “109 Method”, “Le Mond Method” and “Holmes Method,” each with their pros and cons, but let’s start with a basic trick to get a ballpark idea of what is safe. Get on the saddle of your bike and move one pedal to the lowest point with your feet planted flat on it. Check three things:

  • Is your leg on the lowest pedal fully extended and straight, with the foot flat on the pedal?
  • Does your knee stay below the horizontal line when the pedal is at the highest point?
  • Can your toes touch the ground, when you are in the saddle, and the bike is upright?

If the answer to all these is in the affirmative, the saddle height is ideal for you. If not, try changing it until you get all three right. And in the even you can’t meet these three criteria on any seat height on your bike, that means that you need to get a different frame size.

How to Find the Ideal Handlebar Position

Unlike seat height, handlebars cannot be easily adjusted on many bikes. But optimal handlebar height is essential to avoid potential back trouble. The ideal handlebar height is where your entire torso, including arms, hands, neck, shoulders, and back feels very relaxed. For many riders, this is achievable with a handlebar height that is level with, or slightly above the seat height. Take this as a baseline before trying any radical alterations. To find out if your handlebar height is level with your seat height, try the following steps. Take a stick and place it flat on the seat and extend it above the handlebars. Do this if you have made any significant seat height adjustments, to figure out whether you need to make any changes to handlebar height as well.

That, in a nutshell, is what bike sizing is all about. Hope any doubts you may have had about how to measure a bike has been resolved with this bike sizing guide. Check out our biking sizing charts on this site for a more in-depth look at tables of frame sizes and appropriate rider heights.

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