What Size BMX Bike Do I Need

Author: Alex Bristol

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Buying your first BMX?

When you’re trying to figure out which size BMX bike is right for you, you’ll probably find all sorts of measurements given. When you’re a beginner, it’s easy to get lost in the world of bikes sizes and dimensions, but if you’re serious about BMX, it will be worth it when you find your perfect match.

whether you’re buying your first BMX bike or an advanced cyclist and you want to check you’ve got the right size. Learning how to size a BMX bike is key to getting the right fit for you. Once you know what size you need, then you can go hunt down the best BMX bikes.

Listen to this.

In this article, I will discuss everything I wish I had known when picking out my first BMX for myself. From learning what size bottom bracket do I need for my BMX, what size top tube do I need BMX, and what all the little measurements mean so even beginners can have a go.

Most things such as frame size and tube frame can be very different if you don’t know what you’re looking for. In a complete bike, you can have different tube lengths or chain stay length, which affects the bottom bracket and head tube angle as well. Depending on your riding style and height, you’ll want to check out a few things.

Stay tuned.

Why sizing matters

You might think that BMX is the same as any old bike when it comes to size. That’s where you could go wrong. BMXs come in a range of styles, namely because they’re built for speed or to take hard landings and quick maneuvers.

That’s why you’ll find BMX’s often look smaller compared to other bikes for that height or age range. That’s because, depending on your riding style and certain characteristics, you’ll want different sized parts, as well as the fact that BMX bikes come with different components and top tubes than regular bikes people ride.

You might be tempted to go bigger. Don’t. Especially if you do street riding, bigger just means it’s harder to control the bike.

Key BMX Sizes

  • Top Tube (TT) is the most important size when buying a new BMX.
  • Most BMX bikes have 20″ wheels, but you can also find 12″, 14″, 16″, 18″, and 24″ cruisers.
  • The TT length will vary according to the wheel size

Bear in mind when buying a 20″ complete BMX bike, they are likely to still have some different sizes and won’t be one frame size fits all.

The top tube length on BMX bicycles measures the biggest part of the frame from the front of the bike or head tube(HT) and the seat post tube (ST). Although this is the main measurement, it’s a good idea to check out the measurement of the chainstay and bottom bracket as well as the wheel sizes, and if possible to sit on the bike to see how it feels such as the bar position. This is going to give you a better chance of finding the right BMX size for your specific body and preferences and find the difference between them.

What size BMX bike do I need?

Bike sizes have a wide range, depending on your height. It can make a big difference getting the right size for you especially if you’re performing stunts.

You’ll find that most bike brands will make kids-style BMX bikes that are smaller anyway. This isn’t expert advice, but here is an idea of what size to get for your height:

What size BMX bike should I get for my height?

4’4 & above rider

  • Micro mini or Mini
  • Top tube length of 15″-16.5″
  • Stem Length of 30mm-40mm
  • Bar width of 21″-35.5″
  • Gearing of 41-43/16
  • Wheel size 16″-18″ inches

4’6″-5’1″ rider

  • Junior
  • Top tube length of 17″ -19.5″
  • Stem length of 40mm-45mm
  • Bar width of 22″-25″
  • Gearing of 42-43/16
  • Wheel size of 18″-19.5″inches


  • Expert
  • 18.5″-20″
  • Stem length of 43mm-48mm
  • Bar width of 25.5″-27″
  • Gearing of 42-43 / 16
  • Wheel size of 19.5″ – 20.5″inches

5’7″ – 6’0″+

  • Pro xl
  • Top tube length of 20.75″-21.25″
  • Stem length of 50mm-55mm
  • Bar width of 28″
  • Gearing of 44 / 16& over
  • Wheel size of 20.5″- 22″inches

Sizing up for your first modern BMX bike can be daunting, but it’s all a question of trying out what riding style works for you. Not every BMX bike is the same, these sizes are suggestions based on the height of the rider, but at the need of the day, everyone is different.

What size BMX bike should I get

The size BMX you should get depends not only on your height, but also on your riding style. BMX has a variety of categories, but the frame mainly focuses either on racing or freestyle. Here are some sizing options for your riding style:


If you know you’ll be riding your BMX in urban surroundings and doing stunts that involve air jumps and harsh landings, then the right BMX size is either end of the scale. It needs to be strong and sturdy, built well, and can take harsh landings and abuse. This is largely based on your preference, but smaller may be better for clearing the bike when doing tricks or stunts and maneuvering it in the air.


If you like to rid in skate parks, then you’ll need a responsive bike. You can achieve this by going for a short top tube (TT) length, with a shorter chainstay (CS). The head tube (HT) angle should be steeper. If you’re using a sizing chart, try sizing down like a micro mini to get bikes with 20″ top tube for better results.


If your like doing trail or dirt riding, then you’ll require more stability, and therefore a bigger bike is best. Go for a longer top tube (TT) and chain stay (CS) with a slacker head tube angle. This will give you more stability for when doing dirt jumps or riding uneven or rough trails. Riders prefer a top tube length of 21″ fo frame size.

If you’re on a budget or just starting off and getting yourself a complete bike or entry level BMX, then you’ll probably find them somewhere in the middle of the scale. Try out as many as you can at the bike shop or test ride them so you can get a feel for what you like or don’t like in different bikes to get the right one for you. Once you’ve got more experience in BMX, why not try shopping for a separate BMX frame and parts and try your hand at building your own custom BMX?

Final Thoughts

Whether you’re looking for a regular BMX or a freestyle BMX, finding the right size for street riders can be a challenge. Bike size can involve so many things, from the BMX frame down to details like sealed bearings and rear wheel size that even advanced riders can struggle to find what is best for them.

The right size BMX frame is around the corner, whether that’s a micro mini or pro xl frame size for shorter riders or a bigger bike than the suggested BMX wheel size, it’s all your personal preference. The BMX size can vary how the bike feels, and of course, rider height plays a big role too. Most riders will want to check out the wheel sizes and tires as well as top tubes to ensure it matches their corresponding height so its fits perfectly.

The right BMX is right around the corner!

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