Bike frame size guide
There is no single formula that gives the right frame size for every bike. Brands measure their frames in different ways, and two bikes marked “54” or “M” can fit very differently. The reliable method is simple: know your own measurements, then compare them with the size guide of the bike you are looking at.
Three things decide the right size
Your height and your inside leg length are the starting point. Arm and torso length matter too, which is why two riders of the same height can prefer different sizes.
An upright city bike, a singlespeed, a gravel bike or a cargo bike are designed for different riding positions, so their sizing is not interchangeable.
The frame's proportions, not just its size label, decide how stretched or upright you will sit.
How to measure yourself
- Height: stand barefoot against a wall and measure from the floor to the top of your head.
- Inside leg: stand barefoot with your back to a wall, place a book between your legs, spine up and pressed gently upwards, then measure from the floor to the top of the book.
- Compare: check both figures against the size guide on the product page, or the manufacturer's own size chart.
If your measurements fall between two sizes, a test ride or a bike fitting is the best way to decide.
Sizing by type of bike
Usually sized S, M, L or in centimetres, with an upright position. A step-through frame makes getting on and off easier. Urban bikes
Often sized in centimetres and sometimes with a sportier position, so check the reach as well as the size. Fixie and singlespeed
Long rides make small differences noticeable. Compare stack and reach between models, and consider a bike fitting. Gravel bikes
Sized like conventional bikes, by frame size and rider height, according to each brand's chart. Electric bikes
Omnium, for example, offers its cargo bikes in several frame sizes, chosen by rider height. See our Omnium guide.
Chosen by wheel size and the child's height. See our children's bike size guide.
Geometry in a few words
Seat tube length
The traditional “frame size”. Some brands measure it to the top of the tube, others to the centre of the top tube, so the same number can mean different things.
Effective top tube
The horizontal distance between the head tube and the seat tube. It largely decides how far you reach to the handlebars.
Stack and reach
The vertical and horizontal distance from the bottom bracket to the top of the head tube. They are the most useful figures to compare bikes across brands.
Standover height
The height of the top tube above the ground. You should be able to straddle the bike comfortably with both feet on the ground.
Jan Glorie of Glorie Bike Lab.
Bike fitting in Meppel
Choosing a size gets you close. A bike fitting fine-tunes the rest: saddle height and position, handlebar reach and contact points. Together with Jan Glorie of Glorie Bike Lab, we offer professional bike fitting in our shop in Meppel, especially useful for road and gravel bikes or if you feel discomfort while riding.
Frequently asked questions
Can I calculate my frame size from my inside leg?
Rules of thumb exist, but they assume one way of measuring frames and one riding position. Because brands measure differently, the manufacturer's size chart for the bike you are considering is more reliable.
I am between two sizes. Which one should I choose?
It depends on the bike and on how you like to ride. A smaller frame often feels more agile, a larger one more stretched and stable. A test ride is the most reliable way to decide.
Can the bike be adjusted after purchase?
Saddle height, saddle position and often the stem or handlebar can be adjusted within limits. They fine-tune the fit, but cannot fully compensate for a frame that is the wrong size.
Not sure about your size? Come and try, or book a bike fitting.
Visit L'Hirondelle in Meppel
