Mountain Bike Sizing Guide: How to Choose

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a man doing mountain biking

With many riding styles and mountain bike types, each cyclist found a perfect way to satisfy their rough terrain cycling needs. The extreme sport’s popularity gradually increased over time, so much so that there were at least 8.69 million mountain bike riders in the United States alone in 2021.

Mountain Bike Sizing Guide: How to Choose

If you’re planning to partake in such an adrenaline-filled activity, there are a few things you want to consider. For instance, how do you choose the right mountain bike frame and wheel size? What factors should you take into account?

Allow me to guide you through the ins and outs of picking the right mountain bike size.

Different Types of Mountain Bikes

Mountain bikes come in different types that vary in purpose, geometry, suspension, weight, seat posts, etc. Choosing the right mountain bike for you may seem like a daunting task at first, but it eventually becomes easier as you ride and know more about your preferences.

While many manufacturers label their bikes with different names and designs, the four main categories are cross-country, trail riding, enduro, and downhill. Let’s go further into detail about these mountain bikes and their capabilities.

Cross-Country or XC Mountain Bikes

If you’re someone who enjoys going far places with your trusty old bike, cross-country cycling might be up your alley. This discipline incorporates a variety of paths, such as woodlands, fire roads, and flat trails.

Riders who prefer a leisurely activity stick with flat trails, while those who are more competitive go for off-road climbs. I tend to incorporate a bit of both to enjoy the ride while getting a good workout session too.

Cross-country mountain bikes are used more for climbing rather than descending. As such, their design favors lightweight wheels and other materials for faster rolling resistance. While most XC bikes have hardtails, some have a full suspension design to enhance off-road climbing.

back view of a man biking

Trail Riding Mountain Bikes

Trail mountain bikes are one of the most commonly used by off-road cyclists. This design’s versatility makes it useful for just about any kind of terrain or riding discipline. Its build category falls somewhere in between cross-country and enduro mountain bikes.

I find this bike most efficient when I wish to engage in a bit of cross-country or technical singletrack riding without fully committing to it. It’s not as effective as cross-country and enduro mountain bikes, but it does the job well enough to get a glimpse of both disciplines.

As much as this bike is quite agile and versatile, it’s not suitable for singletrack trails of high difficulty. However, it’s a decent place to start for beginners who want to test the waters of mountain biking.

Enduro Mountain Bikes (All Mountain)

Cyclists refer to enduro as a type of mountain bike racing that includes around three to six timed stages. In simplest terms, the goal is to reach the top of a mountain and race to the bottom while beating the clock.

Enduro mountain bikes are optimized to descend rough and steep trails as quickly as possible. However, that’s not to say the bike’s ability to climb uphill is compromised, as it’s also necessary for this discipline.

While it may sound like enduro is only suited for pros, it’s actually quite easy for amateurs to get into. There’s less pressure since you only need to compete with yourself and the clock. To top it all off, you have transition stages to utilize if you need to catch your breath and take a quick break.

Downhill or Park Mountain Bikes

Downhill riding is an extreme version of enduro in the sense that it focuses on descending steep and rough terrain. Unlike enduro races, it doesn’t include any transition stages, only has a single track, and is usually over after a few minutes.

Mountain bikes used for downhill racing require hydraulic disk brakes and long travel suspension. You’ll find downhill bikes stronger and heavier than most designs due to their heavy-duty tires, long-wheelbase frames, and large brake systems.

These bike features are all geared to increase their stopping power for better control in steep and rowdy terrain. The highest-performing downhill mountain bikes often have the most aggressive designs to cater to such an elite riding discipline.

What Are the Different Mountain Bike Sizes?

The size of your mountain bike plays a vital role in riding control and comfortability. It also goes hand in hand with your safety while riding, which is why cyclists take time choosing which size best fits them.

As such, you need to get a good feel of the mountain bike. It’ll serve as an extension of your body as you engage in various cycling activities.

These are the corresponding dimensions of each mountain bike size in inches and centimeters:

Size of the Mountain BikeMountain Bike Frame Sizes in Inches and Centimeters
Extra Small13 to 14 in (33 to 37 cm)
Small15 to 16 in (38 to 42 cm)
Medium17 to 18 in (43 to 47 cm)
Large19 to 20 in (48 to 52 cm)
Extra Large21 to 22 in (53 to 57 cm)
Double Extra Large22 to 24+ in (57 to 61+ cm)

What to Consider Before Choosing a Mountain Bike Size

Any experienced cyclist knows each mountain bike ride differently and has a unique feel to it. You must understand your body proportions, preferences, and height to determine the proper fit before getting a mountain bike.

As much as you can get accustomed to a bike that’s far from your recommended size, it’s best to start with what suits you. This is necessary to avoid certain body pains and unwanted injuries.

On that note, here are what you need to consider before buying yourself a mountain bike:

Rider’s Height

One of the biggest factors to take into account when choosing a mountain bike size is your height. You must follow a proper posture when riding, and the best way to ensure that is by having a mountain bike size that’s proportionate to your height.

Most bike measurements are gender specific, so it’s best to stick to the recommended size according to the rider’s height. Mountain bikes for women tend to be more compact to cater to the female body’s geometry.

These are the recommended mountain bike sizes according to the rider’s height for both men and women:

Rider’s Height (Men)Rider’s Height (Women)Recommended Mountain Bike Size
4 ft 10 in – 5 ft 2 in (148-158 cm)Extra Small
5 ft 3 in – 5 ft 6 in (159-168 cm)5 ft – 5 ft 4 in (152-163 cm)Small
5 ft 7 in – 5 ft 10 in (169-178 cm)5 ft 2 in – 5 ft 7 in (160-172 cm)Medium
5 ft 11 in – 6 ft 1 in (179-185 cm)5 ft 6 in – 5 ft 11 in+ (167-180 cm+)Large
6 ft 2 in – 6 ft 4 in (186-193 cm)Extra Large
6 ft 5 in – 6 ft 6 in+ (194-198 cm+)Double Extra Large

Body Proportions

The body proportions of a rider affect their posture when riding a mountain bike. Since each rider’s body is unique, you need to consider factors such as the length of the arms, legs, and torso.

For instance, the length of your arms can change how you position them toward the mountain bike’s handles. They can also determine the distance of your torso from the head tube.

On the other hand, the length of your legs can affect your comfort while seated and standing on the mountain bike. You’ll have to adjust how you bend them according to how far the bike’s seat is from the pedals.

Riding Style

The only time riders should consider a mountain bike that’s outside the recommended size is when they have a preferred or mastered riding style. Body proportions can also affect your decision, should you wish to down or up a size for your mountain bike.

For instance, a mountain bike with a longer wheelbase will also have a farther reach. This build makes the bike more stable, especially on speedy downhills. I found it easier to ride through rough terrain rather than go around them with this design.

Riders who have long torsos and arms for their height may find it comfier to go with this upsize. The extended reach gives more room to the mountain bike’s cockpit area.

On the other hand, shorter wheelbases sacrifice a bit of stability to increase agility and its ability to flick around. I recommend this build for those who enjoy an active and playful riding style while whipping up BMX (bicycle motocross) tricks.

This design also works for riders with relatively short torsos and arms for their height. The handlebars will be easier to reach and hold comfortably.

What Happens if I Choose the Wrong Mountain Bike Size?

Each mountain bike’s sizing determines its suitability to a rider’s preference, body dimensions, and safety. While most accidents and injuries are caused by incorrect posture and inefficient muscle support, your compatibility with the bike can trigger unwanted troubles.

Choosing the wrong size can cause a lot of discomfort while riding, and you may not be able to enjoy the experience. In severe cases, you might also end up with various pains and injuries further down the line.

Here are some examples of body aches caused by mountain bike sizes that don’t fit you:

  • Knees: Pain in the knees is often a result of saddles placed too high or too low for your height and body proportions.
  • Hips: Similar to how knee pain works, aching hips can be caused by poorly placed saddles, especially if they’re a bit too forward or backward.
  • Back: Your body’s reach from the saddle to the handlebars affects your riding posture. You’ll find your back prone to aching if your mountain bike has the wrong frame size.
  • Arms, shoulders, and neck: Pains around these areas result from a poorly placed saddle, improper stem height, and awkward saddle-to-handlebar reach. It’s a huge indicator that your mountain bike is too big or small for your size.

How to Measure Your Body Proportions

There are a few ways to measure your body proportions according to the mountain bike you wish to use. These measurements will come in handy once you look for your perspective new bike.

2 men doning mountain biking

Follow the steps below to get your body measurements:

Measure Your Reach

  1. If you don’t already know your exact height, you can measure it by standing against the wall and marking the highest point on the top of your head. Ask assistance from a friend if necessary.
  2. Use a tape measure to get the length in centimeters.
  3. Multiply your height in centimeters by 2.55 to get your estimated reach.

Measure Your Rider Area Distance (RAD)

  1. Grab a pencil and measuring tape. Be sure to wear your bike shoes as well.
  2. Stand next to a wall while holding the pencil in one hand. Keep your feet pedal-width apart and your arms bar-width apart.
  3. Stand firmly and roll your shoulders back before marking the wall.
  4. Measure from the ground to the mark on the wall to get your RAD number.

Measure Your Arm Span

  1. Stand straight or against the wall with both your arms stretched out horizontally. Make sure to keep your palms open as well.
  2. Ask help from a friend and have them measure the length from the end of one hand to the other using a measuring tape.
  3. Multiply the length in centimeters by 4.4 and 4.2 to get the range of your max and min arm span.
  4. Your safe bar width will be between the min and max arm span. This measurement will allow your arms to fall into a comfortable position while riding.

Measure Your Backsweep

  1. Grab two pencils and tie their ends with a string the same length as your handlebar’s width.
  2. Keep your shoulders relaxed while stretching your arms in front of you the same distance you would as if you were grabbing the bike’s bars.
  3. Ask a friend to mark the two ends of the pencils against a square edge.
  4. Use a protractor to calculate the angle of your hands.
  5. Select a bar with a back sweep as close as possible to the measured angle. This angle will give your wrists, elbows, and shoulders the best ergonomic fit.

Measure Your Inseam (Inner Leg Length)

  1. Grab a measuring tape, a pencil, and a level (book, pencil case, or any rectangular object with a flat surface).
  2. Remove any footwear and stand straight with your back against the wall.
  3. Place the level between your thighs until your crotch area feels a bit of pressure. Rest the level’s edge against the wall behind you to ensure it’s straight.
  4. Measure the distance between the floor and the top edge of the level and mark it with a pencil. You can use this length to determine the recommended frame height for your leg measurement.

Measure Your Standover Height

  1. Straddle your mountain bike while standing straight. You can wear your cycling shoes while doing this to ensure an accurate standover height measurement.
  2. Check if you have at least two inches of clearance between the tires and the ground. This measurement gives assurance that you can make quick dismounts while on trails.
  3. If you’re an aggressive biker with an active and playful riding style, the standover clearance can go for around three to five inches.

Calculate the Recommended Frame Height Using the Inseam Length

When calculating the recommended frame height, be sure to take note of your inner leg length in centimeters. You can get an ideal seat tube measurement in inches if you multiply your inseam by 0.226.

If you want the value to appear in centimeters, multiply the length by 0.574 instead. You can use these measurements to select the correct mountain bike frame height that’ll support your body proportions.

How to Size Your Mountain Bike According to Your Body Measurements

Once you have your body measurements down, you can compare the results with the mountain bike you’re eyeing. You can do this by finding the bike’s frame size and rider area distance.

Follow the steps below to get these two measurements:

Measure the Size of Your Bike Frame

  1. If you can’t find a size label under the mountain bike’s seat tube, you can always rely on a tape measure.
  2. Measure from the center of the crank axle up to the top of the seat tube.
  3. Use this length in comparison with your inseam length to get a mountain bike frame size that’ll fit you.

Measure the RAD of Your Mountain Bike

  1. Find your perspective new mountain bike and take the stock setup.
  2. Measure its RAD by starting from the center of the crank to the intersection where your hands are placed on the bars.
  3. The RAD of the mountain bike should be as close as possible to your body’s RAD. If the measurements are 20 to 30 mm apart, the bike’s too long for you.

Which Wheel Size to Choose for Your Mountain Bike

The size of your mountain bike’s wheels can also greatly affect your riding style, comfort, and safety. You can’t just go with any size you want without knowing first how they perform and if they suit you as a cyclist.

A family biking together, wearing helmets

Luckily, there are enough size options to cater to almost any riding style you may have. That’s not to say you can’t try other options since you’re free to experiment with each riding experience.

Here are the available mountain bike wheel sizes in today’s market and who they’re best suited for:

  1. 26 Inches Mountain Bike Wheels

The 26-inch mountain bike wheels have been the standard option for cyclists throughout history. When I started getting into mountain biking, it was either these wheels or nothing. In today’s market, however, these are no longer as viable as other options.

Nonetheless, 26-inch wheels are still reliable for maneuverability and narrow trails. I still find them useful when I’m in the mood for some dirt jumps and freestyle tricks. You can also use these for kids’ mountain bikes if you find the 24-inch ones too small.

  1. 27.5 Inches (650b) Mountain Bike Wheels

The 27.5-inch wheels serve as the common ground between the traditional and the bigger wheels. They boast their rollover capability without compromising response time and dynamic riding style. As such, they’re often relied on for longer travels.

If you’re a small rider, the 27.5-inch or 650b mountain bike wheels might be up your alley. It has high maneuverability, its tires are lightweight, and it has faster acceleration.

It does have a few drawbacks, however. 650b wheels tend to have a slow momentum buildup, and their traction is less compared to bigger wheels.

  1. 29 Inches Mountain Bike Wheels

If you’re looking for heavy-duty mountain bike wheels, nothing comes close to the power of the 29ers. These bad boys are a force to be reckoned with on off-road trails, crushing every obstruction in your path.

While these wheels are best suited for tall riders, I find myself enjoying them when I need a boost in confidence for rugged terrain. Of course, you won’t be able to do an active riding style with these wheels, but that’s not what they’re about.

Cross-country bikers will definitely find the 29ers comfortable for long travels. It’s also a great place to start if you’re a beginner cyclist.

  1. Kids’ Mountain Bike Wheels (12 to 24 Inches)

Last but not least, I believe it’s worth mentioning the 12 to 24 inches wheels for kids. After all, anyone can get into mountain biking if they’re passionate enough to learn.

The standard size range of these wheels is enough to give youngsters the training experience they need. They’re also less expensive, so it’s worth investing in if you have kids who are willing to try.

If the 24-inch wheels don’t cut it, they can also go for the standard 26 inches.

Photo of author


Paul Tuthill
Growing up in Scotland, Paul developed a love for the outdoors and a desire for adventure from an early age.