If you’re planning to buy your first mountain bike, you are probably wondering what size to get. The “what size bike for me?” question comes up over and over again, so here is the answer…

What is the ideal mountain bike size for me? I’m 6’3″

What size mountain bike for a female, 5’2″ 120 lbs? I’m looking to get into mountain biking, and I was wondering what size bike frame and what size wheels I need, because of my short height.

Those are just two examples of the questions I hear. It’s usually the same question, but with a different height and weight!

Let’s start by looking at what sizes are out there…

Mountain Bike Frame and Wheel Sizes

In general, mountain bikes are available with frame sizes of Small, Medium, Large, and X-Large. The frame measurement is the seat tube length. A Small frame will usually be a 15″, Medium 17″, Large 19″, and X-Large 21″.

But just as important is a seldom mentioned measurement – top tube (TT) length. The length of the top tube partially determines how far you have to reach to the handlebars while seated. This is actually more important to getting a correctly sized, comfortable bike than any other measurement.

To make things even more complicated, frames vary between manufacturers. Some companies measure differently, and most will have different geometry, leading to very different feelings from the same size bicycle!

For example, I love the feeling of Giant frames in their 18″ size. But on a 19″ Specialized, I almost feel cramped. Crazier still, I have a 21″ Trek frame that I got when I was in middle school (I was maybe 5’5″ tall then.) So your size also depends on which brand you choose!

Some manufacturers such as Trek and Gary Fisher and doing bicycles with geometry specifically for women, so that is an option for some smaller women. If you are around 5′ tall, you may prefer a women-specific design.

The most popular wheel size is 26″. Just about every mountain bike you look at will have 26″ wheels, so there isn’t much to worry about with wheel size.

Gaining in popularity is the 29″ wheel size. A few years ago you rarely saw a 29″ wheel bike, but today, there are actually quite a few 29″ bikes out there. While there is a hot debate about which size wheel is better for mountain biking, I’d say stick with 26″ wheels unless you already know the advantages and disadvantages of 29″ wheels (in which case you probably understand frame sizes as well.)

The only other thing to know is to avoid 24″ wheels in almost all cases. Those are typically found on small mountain bikes at department stores, and replacement parts (tires, tubes, etc.) are hard to find. Only look at bikes with 24″ wheels if you are particularly short and can’t get comfortable on a small 26″ wheel bike.

The Size For You

In general, if you’re short, you’ll get a size small. If you’re tall, you’ll get a larger size. But you also have to consider inseam length rather than just your height. And then your arm length comes into play as well.

All I can really tell you without fitting you on a bike is, “if you are 6’3″, start by looking at the XL size” and, “if you are 5’2″, take a look at bikes in the XS and S sizes.”

It’s impossible to determine your exact size over the internet! Bicycle geometry (not to mention the human body) is too complex and unique to analyze so easily.

Bottom line: There is no “this is the size for you” answer to this question. Anyone that gives you a specific size to get, without discussing specifics about the exact frame in question and seeing your body, is just guessing (and most likely wrong.)

How to Actually Get the Right Size Bike

If you’re serious about getting a proper-fitting mountain bike, you owe it to yourself to visit a bicycle shop. Not a department store, not a sporting goods store, and not an online retailer.

You want to actually see the bikes in person and take them for test rides. What’s cool is that you don’t need to walk into a shop and know exactly what size to get. That’s the point of bike shops – they help you pick the right size bike!

But before you go shopping, here are some tips on bike fit:

It should be comfortable. Comfort is subjective, so it’s up to you to pick out which bicycle seems most comfortable. You should be able to sit comfortably on the bike and reach the handlebars without being too stretched out. Likewise, you might not want to be too upright.

Get some standover clearance. Since mountain biking can be dangerous and there’s always a possibility of crashing, you want to have some clearance. Look for about 2-4″ of clearance between your crotch and the bicycle’s top tube.

Get the smallest bike that still fits. You want the smallest frame you can get that still provides the correct riding position. (To get the correct position, you need to test ride and fit the bike in a bike shop.)

The smaller frame is easier to handle and provides more standover clearance, plus it’s a little lighter and stiffer.

Be wary of certain deals. Some unscrupulous bike shop employees will attempt to sell you a bike that’s a size too big or small in order to clear out old inventory. Even if they offer you a good deal, I don’t suggest getting a bike that doesn’t fit perfectly!

Test ride. Finally, test ride the bikes. It’s about what you like, and a test ride is the best way to figure that out.

Then and only then should you decide on the right size bike!

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7 Comments
  1. Excellent site with bike tips. Learning a lot and finding your site very informative, will be reading much more. Thanks!

  2. @Pilar

    Thanks for stopping by! If there’s something you can’t find, just e-mail me.

  3. I am 6’4″ but I cannot throw my leg over the top tube because I had a hip replacement on both hips due to a shipboard accident in the navy, I can not run anymore either due to the replacement, so I bought a bike that was for my size ,can not swing legs over, so I thought about a mountianbike like a 29er feels right to me, is that right for a person with a hip or hips. or will that be a problem maybe peddling or knees hitting, or is that just too small for 6’4” guy. thanks for any u can give me!!!!

  4. @James

    I’m almost positive you can find a nice 29er that will fit you. At least some will have lower top tubes than a road bike yet still be roomy. I guess you’ll have to find some in a shop to see if they work with your hips!

  5. I’m 5’10, is 26×17 bike frame with 26×1.95 tires good for me?

  6. I’m 5’5″ slim about 50kgs and I was a newbie in bike. Im planning to buy my first ever mountain bike. Is it okay for me to buy a Extra Small size? It is because the brand im looking doesnt have the stock for small only extra small was available. I was talking MERIDA BIG7 300, that was the budget that I have for now. Seeking for a professional advise to avoid injury in the long run. Appreciate your feedback.

    Thank you.-

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