How to Determine the Best Bike Frame Size for You

Bikes are measured in a variety of ways and the information out there can be tricky to navigate, but the most important measurement regarding frame size is the length of the vertical seat tube. In other words, the length of the tube between the bottom bracket and the point where you attach a bike seat is considered the size of the bike frame.

Some bikes are displayed with S, M, L, or XL sizes which can be deceptively simple. The relation between these conventional sizes and the seat tube length can vary between brands, so make sure you consult the size guide for each manufacturer.

Are there major differences between men's and women's bikes? The differences, although subtle, are meant to account for female riders who fall outside the average range of standard bike sizing. Much can be said about the statistics showing that women tend to have shorter torsos, longer legs, and greater flexibility than men, but this varies for each individual. Typically, however, the frame geometry of women's models will have a shorter standover height and shorter reach. Contact points are also dialed-in to accommodate average female preferences, resulting in relatively narrow handlebars and saddles that are wider and shorter than their male counterparts.

So if you're a woman, does that mean you need a women's frame? Not necessarily. Everybody is different and everyone has their own riding style and comfort preferences. For all intents and purposes, bike frames are fundamentally unisex so your primary focus should be finding a bike frame that fits your body and your needs.

You might find yourself asking, "How do I know when my bike frame is too big?" or "How do I know when my bike frame is too small?" Great questions. An improper frame size can compromise your comfort and performance, as well as your safety and the safety of others.

The easiest way to locate your goldilocks zone for frame size is by using height, inseam, and standover height measurements.

1. Height: This one is pretty easy. If you don't already know your height, stand up straight against a flat wall and use a tape measure or yardstick to find your height. Ask a friend for help if need be.

2. Inseam: Stand up straight with your riding shoes on, plant your feet no more than a foot apart, and measure the distance along the inside of your leg from your crotch to the floor.

3. Standover Height: The standover height of a bike is the distance between the ground and the top of the top tube. Manufacturers and retailers usually provide the standover height measurement in their online product specs, so no sweat if you don't have the bike right in front of you. Compare the standover height to your inseam measurement to make sure both feet are stabilized on the ground when standing over the bike. As a general rule of thumb, you should shoot for at least an inch of clearance above the top tube.

Traditionally, manufacturers will size road, gravel, and cyclocross bike frames in centimeters and their mountain and hybrid frames in inches. Keep in mind that bike frame geometry is dictated by the style and primary use of the bike. It's common that your mountain bike would be a frame size smaller than your road bike for better handling on aggressive terrain.