Mountain Bike Sizing Guide

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The right mountain bike size instantly gives you more control and leads to more comfort and more confidence on your rides.

Here’s some general advice for getting the perfect mountain bike size:

  • Something you should know about your skills and abilities if you struggle with mountain biking: maybe it’s not you. It could be that your bike isn’t the right size, which can make it hard to handle.

  • If you’re just starting out as a beginner mountain biker, getting the bike size right from the start can make the difference between loving the meditative flow of cleaning a technical piece of singletrack for the first time, or angrily chucking your mountain bike after too many failed attempts.
  • You could get the best state-of-the-art mountain bike for your money, but if it’s the wrong size, it will lose its bling in no time compared to a cheaper one that’s the right size. First however, maybe you want to know what type of mountain bike you need, which will help start to narrow down your choices.

Before you invest in a new (to you) mountain bike, read on for valuable advice about:
  • What size mountain bike do I need?
  • How are mountain bikes measured?
  • How to get the best mountain bike fit (pros and cons of sizing up/down)
  • Mountain bike geometry measurements
  • What problems are caused by a mountain bike that’s the wrong size?

What size mountain bike do I need?

A mountain bicycle that’s too big can make cornering tough for maintaining your line, and a bike that’s too small has a mind of its own on technical trails.

Buying the wrong size can also cause many physical issues, including muscle pain, inability to ride for long periods of time, and increased chance of injury. If it were as simple as picking a small, medium, or large mountain bike, you could simply throw your leg over the saddle and off you go, no need to get down in the weeds about bike sizes.

The reason to pinpoint a precise size is to gain sheer riding comfort and enjoyment because you’ll be a lot happier on a bike that’s a perfect fit.

The following mountain bike size chart will give you a good idea of the numbers that underlie mountain bike sizes.

Frame Size

Rider Height (in)

Rider Height (cm)

Frame Size (in)

Frame Size (cm)

XS

4' 10" - 5' 2"

148cm - 158cm

13" - 14"

33cm - 37cm

S

5' 3" - 5' 6"

159cm - 168cm

15" - 16"

38cm - 42cm

M

5' 7" - 5' 10"

169cm - 178cm

17" - 18"

43cm - 47cm

L

5' 11" - 6' 1"

179cm - 185cm

19" - 20"

48cm - 52cm

XL

6' 2" - 6' 4"

186cm - 193cm

21" - 22"

53cm - 57cm

XXL

6' 4" +

194cm +

23" +
58cm +

The difference between sizes is the seat tube length, which has historically corresponded to the frame size, but since mountain biking has evolved into multiple riding disciplines, one size really doesn’t fit all.

Now you have mountain bikes for gravity riding, cross-country, all-mountain, down mountain etc. and each bike is designed to meet rider demands for specific performance characteristics. Still, you have to start somewhere, so check out a size chart to see where you land in the wide world of mountain bike sizing.

Women’s mountain bike size charts

Whereas women’s road bike sizes are still expressed in universal terms, some women’s mountain bikes are designed using women’s body dimension data to produce bikes specifically for women. This may result in shorter or more compact frame dimensions to accommodate a shorter torso and longer legs.

It wouldn’t hurt to do a little investigation into brands that claim to supply bikes for women because it may just be that the components and finish are all that change for a bike to be specifically for women.

Along those lines, a lot can be done to a unisex frame, like installing narrower handlebars or a biometrically fit saddle, to make it supremely comfortable for the rider no matter the gender.

 

How are mountain bikes measured?

The traditional method to determine mountain bike sizing was to simply measure from the center of the bottom bracket to the top of the seat tube.

Most mountain bikes also focus on a low standover height, which doesn’t really work if the recommended standover height is the distance from the ground to the top of the top tube + 2.5 cm/1 inch of clearance between you and the top tube. If you follow this outdated fit indicator, you could end up with a gigantic bike!

Both of these methods fail to take into account the rider’s flexibility and range of motion in the hips, as well as the rider’s preferred position on the bike, which are crucial pieces of information for current trends in mountain biking. Thanks to the ever-evolving ways in which people are riding off-road, these methods have become obsolete.

What makes mountain biking so magnetic is what also makes mountain bike sizing so particular, and that’s its multiplicity.

New methods for mountain bike sizing beg for a deeper customer analysis to find out what type of terrain the customer typically rides, what’s his or her riding style and average ride duration.

New tube shapes, highly engineered components, and proprietary frame dimensions* all have an impact on a mountain bike’s size, which is why you would be best served with actual facts about how a particular mountain bike would uniquely fit your body, terrain, style, environment, endurance, and budget.

There’s a lot to gain from speaking with an expert – someone who exists in the world of bikes and knows all the ins and outs (plus the quirks, hidden knowledge, and frustrations) of mountain bike sizing.

To get the actual facts, it literally costs you nothing to book a video call with an expert advisor. You can choose the expert who best suits you for a 20-minute chat to answer all your size questions.

Here’s how it works:

  1. Choose an advisor and a time slot that works best for you.

  2. Answer a few quick questions on your level of cycling experience.

  3. Your consultation is confirmed! At the time of your meeting, you’ll join using a Microsoft Teams link provided by Cycling Avenue.

*Although manufacturers provide bike geometry and height charts to make it easier for buyers to pick the right size, not all manufacturers use the same sizing schemes. That’s why it’s recommended to read the specifications carefully and pick a bike that corresponds to your own body and riding style.

How to get the best mountain bike fit

A bike that’s a perfect fit also helps you ride more efficiently, avoid injury, and makes riding a whole lot more fun. Understanding how the bike’s size affects the way you ride will also help you zero in on your perfect bike because with the right size bike, you’ll instantly have more control.

There’s lots that can be done to a mountain bike to customize the fit, like swapping out the fork, handlebar stem, cranks, saddle, pedals, and tires, which may compromise their performance if they’re making up for a frame that’s the wrong size.

It’s easier (and cheaper) to start by getting a frame that fits your proportions. If you’ve discovered that you’re in between sizes according to the manufacturer’s bike size chart, you’ll want to know the pro’s and con’s of sizing up or down.

Pro’s and con’s of sizing up

  • Size up if your home trails aren’t overly sinewy and technical, and you like to dominate your terrain like a monster truck, then go ahead and go big(ger). A bigger bike with a longer seat tube doesn’t just raise the bike up, it also tends to stretch the bike out, or increase its “reach.”
  • Reach is the horizontal distance from the center of the bottom bracket to the center of the head tube.
  • If you are long in the torso area and have long arms, you may find that a longer reach gives you more space and a more comfortable cockpit. Too long though, and you’ll be too stretched out, which can cause lots of physical problems.
  • Extending the bike’s reach also lengthens the bike’s wheelbase, which is the horizontal distance between the center of the front and rear axles. In theory, increasing the wheelbase will increase stability, whereas shortening the wheelbase will make the bike more maneuverable.

Pro’s and con’s of sizing down

  • Size down if you want a nimbler ride that reacts to abrupt changes in terrain. The shorter reach and shorter wheelbase on a smaller bike will also give you a more casual, upright riding position good for long stints in the saddle.
  • If you have a short torso and perhaps lack a bit of flexibility, a smaller bike with a shorter reach would put you more in control, should you need to react quickly. Too short and you may lose mobility because you’ll be too upright.

Of course, lengthening or shortening the seat tube, increasing (or decreasing) reach, and altering the wheelbase all impact the way the bike rides, and if we all rode mountain bikes the same way, the outcome would be predictable, and we wouldn’t need to bother too much with…

 

Mountain bike frame geometry measurements

The dimensions and angles that make up a mountain bike are its frame geometry, and they matter when it comes to the bike’s fit and feel (and style). Frame geometry is also conceived for the terrain that the bike is intended for, so while you don’t need to know the exact measurements for a specific type of bike, you do need to know what type of bike you want.

Once you determine your riding discipline, you can compare mountain bike frame geometries from one brand to another because subtle differences would be worth investigating.

These are the main measurements:

  • Effective top tube – the distance in a straight line from the center of the head tube to the seat post. Because nearly all mountain bike top tubes are sloping, the effective top tube length would give you an idea of how long or short your overall reach would be.
  • Head tube angle – the angle between the mountain bike’s front fork and the ground. A slacker head tube angle can be found on gravity bikes whereas a steeper angle is more characteristic of cross-country bikes.
  • Chainstay length – Length of the two thin tubes that run parallel to the ground on each side of the wheel from the hub to the pedals.
  • Bottom bracket height – the distance from the ground to the center point of your cranks.
  • Wheelbase – the horizontal distance between the center of the front and rear axles.
  • Seat height – the vertical distance from the center of your bottom bracket to the top/center of your saddle.
  • Saddle position – the placement of the saddle relative to your knee in the six o’clock position of a pedal rotation. Knee alignment (not reach!) is key to avoiding discomfort or injury.
  • Handlebar height – relative to your saddle height, your handlebar height should be adjusted to ensure relaxed shoulders and neck, slightly bent elbows, straight back, easy access to shifters and brake levers, and general overall comfort.

It’s important to note that a mountain bike’s fork isn’t part of the frame, but it can significantly impact your ride quality.

Unlike a road bike, where the fork often complements the bike in terms of aerodynamic performance, comfort, and aesthetics, a mountain bike’s suspension fork is a separate component and can be selected based on desired performance characteristics. For instance, some forks are designed for shorter travel, some for longer. There’s also different suspension technology to choose from.

These all affect the way the bike rides and, while it’s uncommon to choose a bike based on its fork, you can choose a different fork from the one that came with the bike. So, that’s why mountain bike sizing is radically different from road bike sizing, and that versatility makes “mountain biking” a catchall title for a club with lots of members.

If you’ve read this blog up to here, you’ve absorbed a lot of information about mountain bike sizing. Take it or leave it, there’s one final bit of advice you need to have.

What problems are caused by a mountain bike that’s the wrong size?

If you end up choosing the wrong sized mountain bike, problems that may be imperceptible at first can develop over time and cause huge problems farther down the road (or trail).

A mountain bike that’s not size: YOU can also compromise stability and performance, which will strip all the fun out of mountain biking. Here are the pending pains you can expect with a bike that's a bad fit:

Knee: pain in this joint often comes from a poorly positioned saddle (too high/low, too far fore/aft), or can be a direct result of improperly adjusted cleats.

Back: if you have pain here, it can be an instant clue to a frame that’s the wrong size and, while there’s no quick fix for that, some mountain bikers have been able to alleviate back pain by changing saddle height or handlebar position.

Hips: saddle position is again the main culprit so something to remember is that it’s “evolution not revolution.” Play around with your saddle position until you can ride comfortably for long periods. Your hips (and back and knees) will love you for it.

 

Mountain bike size shopping advice:

Prioritize the right mountain bike size when shopping for a bike and get more value out of it when you enjoy every single ride. Before you buy, consider these shopping tips:

  • Your bike should fit you, your riding style, and where you currently ride. It’s Ok to upgrade to a dual-suspension if you’ve been riding a hard-tail (or vice versa), just be self-aware of your skills and ambitions and how you plan to evolve them.
  • Get the right frame size. Mutton dressed up as lamb is still mutton, and if you don’t get the right-sized frame from the start, pimping your ride with component upgrades will never make up for a frame that fits.
  • Consult an expert. If in doubt about what’s the right mountain bike size for you, don’t guess, ask an expert for advice.
  • Fine-tune your fit. Make this a work-in-progress on every ride when you get your new mountain bike. Pay attention to the three contact points (hands, feet, seat), make adjustments as needed, and make your comfort priority #1.

If you plan on buying a used bike online, you can find all the information in our how to buy a used bike online article.

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Further reading

5 Reasons Why You Should Buy a Used Bike

If you’re in the market for a bike, you may be wondering what the benefits are to getting a new bike or one that’s simply new to you. For starters, buying a second-hand bike is a far simpler process than buying say, a used car because it’s a lot easier to assess a bike’s condition without having to “look under the hood” for chassis or transmission failures.

Top 7 Mountain Bike Maintenance Pro Tips

Knowing how to maintain your mountain bike will help it last longer and save you money. Plus, when you take care of your own bike, you’ll enjoy riding it even more. Basic mountain bike maintenance isn’t only handy knowledge to have, it’s practical and pays you back in less time (and money) spent at the bike shop getting your bike repaired.