Bike sizing
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How to choose the right bike size
Selecting the right bike size can greatly enhance both your comfort and performance. Bicycle measurements aren’t universal—they depend on both the rider (men's or women's bike sizes) and the type of bike you’re purchasing (road bike frame size, MTB frame size, etc.).
To help you determine your ideal bike size, Bikeroom offers a calculator. This tool allows you to quickly identify your measurements, including inseam length, bike frame height, bike length, and more.
Easily configure your bike in just a few simple steps and get ready to choose from a range of frames— road bike, MTB, gravel bikes, e-bikes, and much more.
The basics
What does bike size mean?
With Bikeroom’s bike size calculator, selecting the correct bicycle frame size is quick and easy. Keep in mind, however, that the calculator provides an approximate estimate, as precise measurements vary depending on brands and models. Bike sizes are typically labeled progressively (from XS to XXXL) or numerically (depending on the manufacturer). Additionally, factors such as body type and personal preferences play a significant role in finding the perfect frame for your needs.
Road bike vs Mountain bike sizes
Understanding bike measurements
For road bikes, frame sizes are usually specified by the length of the seat tube and the top tube (measured center-to-center). These two measurements are often identical, but when different (e.g., 52×53), the first number indicates the top tube length, and the second refers to the seat tube length.
For MTBs (Mountain Bikes), sizes are generally expressed in inches, indicating the seat tube height (from the center of the bottom bracket to the top of the seat tube). Due to the sloping top tube design typical of modern MTB frames, it's challenging to measure the top tube traditionally. Instead, manufacturers provide the measurement for the “virtual top tube length,” which compensates for the angled design.
Bicycle inseam measurement
How to choose the right bike size
As discussed earlier, there are several ways to select the correct bike size, but the most reliable method is based on your inseam measurement. Our bike sizing calculator determines the appropriate frame dimensions using the measurement of your inner leg length.
To find the recommended bike size, you first need to measure your inseam—the distance from the floor to your crotch, where your legs meet your torso.
How to measure your inseam correctly
Take a tape measure and a small rigid object, like a hardcover book.
Stand barefoot with your back straight and heels against a wall. Maintain a gap of about 15–20 cm (6–8 inches) between your feet, and keep your gaze level.
Place the hardcover book between your legs to simulate a bike saddle.
Have a second person measure the distance from the top edge of the book to the floor in centimeters—this is your inseam height.
Unsure between two bike size?
Find the optimal configuration
The Bikeroom bike configurator calculates bike size by taking into account both your overall height and inseam length, two key parameters that differ between individuals, regardless of gender. If you're unsure between two bike sizes, follow this guideline.
Inseam taller than half your height?
Choose a larger size.
Inseam shorter than half your height?
Opt for a smaller size.
For racing, go for a smaller size for better control and aerodynamics.
For comfort, pick a larger size for a relaxed ride.
NOTE: while our bike configurator provides a highly accurate estimate of frame sizes, we always recommend a professional biomechanical analysis to ensure the perfect fit.
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