Mountain Bike Sizing and Fit

Mountain bikers race along mountain pathway
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For the best handling, comfort, and safety, you need to find the right size mountain bike for you. If you know your height and inseam measurements, you should be able to determine what size frame will be most comfortable. Of the two measurements, inseam is more important.

Mountain bikes are generally measured in frame size (inches), which is the distance from the center of the crank to the top of the frame at the seat tube.

Mountain Bike Sizing Guide

When buying a bike, the fit is the most important factor when it comes to comfort—and the more comfortable you are, the more likely you are to keep riding. A bike that is too small will quickly grow uncomfortable, cause handling problems, and will frustrate you. A bike that is too big is also uncomfortable to ride and can be dangerous if you struggle to manage its size, especially on rough terrain.

Your Height Your Inseam Length Bike Frame Size Descriptive Frame Size
4'11" - 5'3" 25" - 27" 13 - 15 inches Small
5'3" - 5'7" 27" - 29" 15 to 17 inches Small - Medium
5'7" - 5-11" 29" - 31" 17 to 19 inches Medium
5'11" - 6'2" 31" - 33" 19 to 21 inches Large
6'2" - 6'4" 33" - 35" 21 to 23 inches XL - Extra Large
6'4" and up 35" and up 23 inches and up XL - Extra Large

As you can see from the chart, mountain bike frames are measured in inches. Sizing goes from about 13-15 inches, which is what someone on the small size might ride, up to 23 inches and above, which is best-suited to a taller rider.

In general, a bike will be about the right size if the top tube (the bar that goes between the seat and the handlebar) leaves two or three fingers of space below your groin (i.e., the inseam of your pants) as you straddle your bike with your feet flat on the floor.

If there is no top tube, sit on the seat. You should be able to touch the ground with your feet, but only on tippy-toes, and even then maybe just on one side or the other. Note that mountain bike frames are generally smaller than road bike frames. The smaller size is intended to make them easier for you to handle on rough terrain.

If you are able to put both feet on the ground while you are sitting on the seat, the bike is too small or the seat is too low, or both.

When sitting on the seat, you should be able to rest your feet comfortably on the pedals, and you should be able to reach the handlebars comfortably without either being scrunched too close or stretched too far out as you lean forward.

Try Before You Buy

Until you feel fairly confident about what size bike is going to be right for you, try one in person at your local bike shop. That's the best way to make sure you are buying a bike that fits you properly.

You’ll be able to try out a range of sizes to see what feels best. Plus, the experts there will be able to tell if the bike you are considering is too small or too big. They’ll also know other adjustments that can be made to improve and fine-tune the fit of the bike even more, once you have the right size mountain bike. These extra adjustments might include raising or lowering the seat, moving it farther back or more forward, and adjusting the height of the handlebars.

There is nothing more satisfying than zipping around on a bike that fits you perfectly. Such a bike becomes an extension of your own body, so it’s definitely worth putting in the time and effort to find the one that is just the right size for you.