How to Size a Mountain Bike : Follow These 5 Steps

How to Size a Mountain Bike

Are you wondering what size of a mountain bike is the best suit for you? There are ways that you can use to determine a befitting size. Test-driving is the best way to actually tell whether a mountain bike is the perfect size. However, if you happen to buy a less than ideal size of a mountain bike there are a few adjustments you can make to make it suitable. Below is a guide on how to size a mountain bike.

Factors That Affect Your Mountain Bike Size

Before we delve into the actual sizing, let’s look into the factors that determine your suitable size for a mountain bike. The right size of a bike depends on your riding style, preference, height and the type of bike.

For example, a rider who prefers speed would be better suited with a small bike to enhance energy and power efficiency. On the other hand, a cross-country racer would be best suited to ride a flat bike a larger size than that which they would normally take.

The bike type sizing standards varies. For instance, hybrid mountain bikes are usually 3-4” bigger for the same rider height.Generally, the hard tail bikes and full suspension bikes are sized the same.

How to Size a Mountain Bike

There are various methods to properly size a mountain bike. They include using a sizing chart, determining the ideal seat the size and frame size, and doing the stand over test. Ultimately, the feel of the bike when you actually ride it should be your guide.

Below are the things you will need to determine your mountain bike size:

  • Tape measure
  • One other person to help you with the measurements
  • Bicycle
  • Wrench
  • Sizing chart

1. Using a Sizing chart

Rider’s height(ft/in) Leg inseam(in) Suggested frame size
4’10’’-5’1’’ 24-29” XS
5’1’’ -5’5’’ 25-30” S
5’5’’ -5’9’’ 26-31” M
5’9’’ – 6’0’’ 27-32” L
6’0’’ -6’3’’ 28-33” XL
6’1’’ – 6’6’’ 29-34”7 XXL

How to Measure Rider’s Height and Leg Inseam

Rider’s height is the actual height of the rider from head to toes when standing upright. On the other hand, the leg inseam is the height from the groin to the toes when standing upright.

To measure your height remove your shoes and stand straight with your feet up to 20cm apart against a wall. Let your partner measure your height with a tape measure from the ground up.

To measure your leg inseam, place a book between your thighs. Stand straight against a wall. Again, let your partner measure your height from the groin to the toes.

Use you height measurements and leg inseam against the size chart above to determine your mountain bike size.

2. Determining Your Mountain Bike Size With the Frame Size.

Another method to determine you mountain bike size is your inseam length to determine your frame size. This is calculated using the following formula:

Leg inseam (cm) x 0.66 = your frame size

3. Determining Your Mountain Bike Size With Seat Tube Length

In addition, you can determine your seat tube length using the formula below:

(Leg inseam (inches) x 0.67) – 4 = your seat tube length

4. The Stand Over Test

This is a simple yet practical way to determine whether a bike is the right size for you. To do the test, straddle the bike and seat on the saddle. Ensure that your feet are comfortably placed on the ground with an allowance of about 2’’. If the allowance is too big or your feet are hanging when you are seated then it is not the appropriate fit.

5. The Perfect Feel is The Best Size

Use your body to determine the perfect size. In an ideal size, your arms and shoulders should be relaxed with the elbows slightly bent. When you are straddled, your heel should touch the lower pedal when the pedal is on the lower stroke. When the pedal is at the top of the stroke, the knees should be slightly bent. Test-drive the bike and let the feel on your body tell you whether it is a good size or not.

Making Adjustments

There are 3 main adjustments you can make on your mountain bike to make it fit better.

  • Seat height adjustment: Using a wrench, loosen the bolt that holds the seat post. Using a tape measure, measure the seat tube to the idea measurements. Swivel the seat post either up or down until you achieve the ideal measure. Use the wrench to secure the bolt.
  • Adjust the handlebars: Loosen the bolt that attaches the handlebar to the frame. Lean forward to a comfortable position. Raise or lower the handlebar accordingly then tighten the bolt at the base of the handlebar.
  • Adjust seat tilt: Sometimes all you need to achieve the perfect fit is to adjust the seat tilt. Tilt the saddle slightly up and down until you achieve a good tilt. Avoid a tilt that will make you slide forward and back.

Once you are done with the adjustments, test drive to ensure you have gotten the perfect fit.


The correct fitting bike will offer comfort and efficiency and you will enjoy your rides. The wrong fit could cost you efficiency or cause injuries. 

Casey Ames

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