Bike Size Calculator (Using Height)

How to Use this Bike Size Calculator

The calculator is quite easy to use, here is what you need to do:

1. Select the unit system as either imperial (ft, in) or metric (cm)
2. Specify the bike type (road, city, mountain or children bike)
3. For the road bike, specify the riding style (if unsure, keep it as ‘neutral’)
4. Input the person’s height to get an estimate of the inseam
5. Input the person’s true inseam, not the pants inseam, (if unsure, use the middle number in suggested range)
6. Press the ‘Calculate’ button to get the recommended frame size (or wheel size for children’s bike)

Please note that the height is not required for the calculation but it helps when you don’t know the inseam or you want to confirm if the inseam number you have makes sense.

Also, you will get a warning if the inseam is too big/small (i.e. doesn’t make sense) or it doesn’t fall under the estimated inseam for the height inputted. This minimizes the chance of getting an inaccurate bike size.

The Way to Measure the True Inseam

As noted above, the inseam used for calculating the appropriate bike size is slightly different than the pants inseam. The true inseam is actually a little shorter.

So, if you utilize the pants inseam for picking the bike size, you will be overestimating the inseam that should be used. This could lead to grabbing a bicycle that doesn’t give you sufficient standover clearance.

Follow these simple steps to measure the cycling inseam:

1. Stand tall against a wall
2. Place a hardcover book between your legs at the top
3. Measure the vertical distance between the top of book and the ground

That number is the inseam you use for bike sizing.

How the Bike Size Calculator Works

The calculator above uses formulas for calculating the frame size for road, mountain and city bikes and a size chart for calculating the wheel size for children’s bikes.

Here are the formulas:

• Road/Gravel/Touring bikes: Frame Size (cm) = Inseam × 0.67
• Mountain bikes: Frame Size (cm) = (Inseam x 0.67) – 10
• City/Hybrid bikes: Frame Size (cm) = (Inseam x 0.67) – 7

The formulas for the first two bike types were retrieved from the book Greg LeMond’s Complete Book of Bicycling. It has a wealth of practical information on bicycling including how to pick a bike, bicycle fitting, cycling techniques, cyclist’s diet, bicycle maintenance, and history of cycling.

The formula for city/hybrid bikes was developed by us based on their size charts and the other two formulas.

The size chart used for computing the bike size of kids’ bicycles is the following:

Please note there is a wheel size instead of frame size for children bikes. Also, the units used for wheel size is millimeter (mm) rather than centimeter (cm).

Main Types of Bikes

While there are many bicycle types out there, we only incorporated a limited number in the calculator above (basically bikes that people tend to use). Here is a brief description of each:

• Road bike: built for traveling at speed on paved roads
• Touring bike: designed for bicycle touring and long journeys
• Gravel bike: intended for riding on gravel and other rough terrain
• Hybrid bike: a blend between the mountain and racing style bicycles
  • City bike: a hybrid that’s optimized for the rough-and-tumble of urban commuting
  • Trekking bike: a hybrid with all the accessories necessary for bicycle touring
• Mountain bike: designed for off-road cycling

For the first three types, the frame size directly impacts reach and posture. So, we included an adjustment based on the riding style:

• For an aggressive riding, we decrease the frame size by two centimeter for a lower, stretched position (for racing)
• For a comfort riding, we increase the frame size by two centimeter for easier dismounts and an upright posture (for enduring)

We haven’t included this in the options for hybrid bikes (city/trekking) and mountain bikes. Because for those, the riding style affects bike components (stem length, handlebars), not frame size.

Tips for Bike Sizing

Here are some important things to consider while choosing the bike size (and using the above calculator):

• Bike Type: The riding purpose will dictate what type of bike to get. For instance, you may pick mountain bikes for off-road trails and a hybrid bike for commuting.
• Inseam: The main deciding factor for nailing the perfect bike size is inseam (true inseam, not pants inseam). The rider height should be merely used as a guide for estimating the inseam if needed. This is the case with the above calculator, by the way.
• Standover Clearance: There should always be a minimum of one inch of standover clearance no matter what type of bike you choose. This is the distance from the inseam to the top tube. For extra safety reasons, some types require even more clearance including the hybrid bikes (2″ or 5 cm) and mountain bikes (4″ or 10 cm).
• Size Variation: Bike size specifications may vary considerably between brands for the same frame/wheel size. So, it’s important to always check the manufacturer’s size charts before purchasing.
• Size Fit: To confirm that the bike fits you and your body, there is really no alternative to actually testing it in-person. Some local shops may even allow you to do a test drive which would be quite helpful.

Conclusion

We hope the above bike size calculator was helpful for buying your next bicycle, whether for yourself or for a loved one.

Before inputting any number in the calculator, remember first to select the preferred unit system (ft,in or cm), bike type and riding style (if shown).

While the rider height is not required for the calculation, it will help you to get an idea of the expected inseam which you will ultimately need to input.

Feel free to let us know if you find anything in the tool that’s inaccurate so we can correct it. Also, we would love to hear any suggestions or questions about it.

FAQ