Bike Frame Size Calculator
Measure barefoot, standing straight against a wall
Stand barefoot, place a book spine-up between your legs, measure from floor to the book's top
Comfort = size down for upright position; Performance = size up for aggressive fit
Enter Your Measurements
Select your bike type, enter your height and inseam, then click Find My Frame Size to get your recommended frame size, saddle height, and wheel guidance.
How to Use This Calculator
Measure Your Inseam
Stand barefoot on a hard floor. Place a hardcover book spine-up between your legs and slide it up firmly against your crotch (as a saddle would). Mark the wall at the top of the book's spine, then measure from the floor to that mark. This is your inseam length — the most critical input for accurate frame sizing.
Select Your Bike Type and Units
Choose Road, Mountain, Hybrid/City, or Kids from the bike type buttons, then select your preferred unit system (metric or imperial). For kids' bikes you only need height — inseam is not required. Each bike type uses a different sizing formula and sizing convention, so selecting the correct type is essential.
Enter Height and Inseam
Enter your height (in cm, or feet and inches) and your measured inseam length. In imperial mode, height uses two fields for feet and inches separately. The calculator auto-calculates as you type — no need to press the button, though you can click Find My Frame Size to confirm.
Review Your Results
Your recommended frame size label (XS–XXL) and frame measurement are displayed at the top. Below that you will find alternative sizes for comfort or performance riding, saddle height, crank length, wheel size guidance (for mountain bikes), and a full sizing reference table with your recommended size highlighted. Use all of these together to make a confident buying decision.
Frequently Asked Questions
How do I measure my inseam accurately at home?
Stand barefoot on a hard floor with your back against a wall. Take a hardcover book and place it spine-up between your legs, pressing the spine firmly upward against your crotch — mimicking the pressure of a saddle. Have someone mark the wall at the very top of the book's spine. Measure from the floor straight up to that mark with a tape measure. This is your inseam. Avoid measuring over clothing, and make sure your feet are about 15–20 cm apart, which is a natural pedalling stance. Repeat the measurement twice and average the results for accuracy. Inseam is typically about 45–47% of your total height.
Why does mountain bike sizing use inches while road bikes use centimetres?
This is a historical convention. Mountain biking originated in the United States, where the imperial system is standard, so early MTB manufacturers sized frames in inches. Road cycling developed in Europe, where metric measurements dominate, so road frames were sized in centimetres. The conventions stuck as each discipline globalised. To complicate things further, many modern mountain bike brands now use letter codes (S, M, L, XL) instead of inches, partly to avoid confusion with wheel size (26", 27.5", 29"). Our calculator displays both measurements so you can match whichever system a specific manufacturer uses.
What if my measurements fall between two frame sizes?
Falling between sizes is common, and the right choice depends on your riding style and body proportions. If you ride mainly for leisure, commuting, or prefer an upright, relaxed position, choose the smaller size — it will feel more natural and easier to manoeuvre. If you ride for sport, fitness, or performance and prefer a stretched, aerodynamic position, the larger size typically suits you better. Body proportions also matter: if you have a long torso or long arms relative to your height, size up. If your arms are short or your torso is compact, size down. When in doubt, visit a local bike shop to test-ride both sizes.
Does the same frame size fit men and women?
Modern bicycle design has largely moved away from gender-specific frames. Today's performance road, mountain, and hybrid bikes are designed around geometry rather than gender, and sizing tables apply equally to men and women with the same inseam and height. Women-specific geometry (WSD) bikes do exist and typically feature shorter top tubes, narrower handlebars, and shorter crank arms to suit riders with shorter torsos, narrower shoulders, and different hip angles — but the frame size number or label is determined by the same inseam-based formula. Our calculator is gender-neutral by default, reflecting industry consensus that body measurements matter more than gender.
How do I know if my current bike frame fits properly?
A correctly sized frame passes these checks: you should have 1–2 cm of standover clearance over the top tube on a road bike, 2–5 cm on a hybrid, and 5–10 cm on a mountain bike. When seated with your heel on the pedal at the bottom of the stroke, your leg should be fully extended without your hip dropping. When riding normally (ball of foot on pedal), you should have a slight bend in the knee — about 15–20 degrees. You should be able to reach the handlebars without fully extending your arms or hunching your back. If any of these are off, adjusting saddle height, stem length, or seat post position can help before considering a different frame.
Are bike sizing calculators accurate enough to buy online without test-riding?
Formula-based sizing is highly reliable for most riders who fall within standard proportions — the vast majority of cyclists get excellent results from an inseam-based recommendation. However, buying without test-riding carries some risk, especially for higher-end bikes where geometry varies meaningfully between brands. Always check the specific manufacturer's geometry chart for stack and reach measurements, not just frame size. Read return and exchange policies before purchasing. If you have a history of back pain, knee injuries, or unusual body proportions (very long or short torso, wide or narrow hips), a professional bike fitting session is strongly recommended before committing to an online purchase.