How Are Bikes Sized?

This AI picture is extreme but shows the importance of getting a bike with the correct size for you. Bikes are sized to match a rider’s height and body proportions, so the bike feels comfortable and safe to ride. The exact system differs between brand and type of bike. You can often fit 2 sizes of a bike,and so making the right adjustments for you will make all the difference. We recommend referencing the brand’s sizing chart for the most accurate info of each bike.

1. Frame size (the main measurement)

This is the most important part of general bike sizing.

• Adult bikes are usually sized by the frame:

  • Road bikes: measured in centimeters (e.g., 52 cm, 56 cm)

  • Mountain bikes: measured in inches (e.g., 15″, 17″, 19″) or sizes like S, M, L, XL

The frame size usually refers to the length of the bike’s seat tube, but more modern geometries focus on the reach or top tube length. These measurements affect how you are positioned on the bike while riding.

2. Rider height (and inseam)

Most brands use height ranges to recommend sizes. For example:

• Someone between 5’4″–5’10” might fit a Medium

• Someone 6’0″ might need a Large or XL

Inseam (leg length) also matters, especially for road bikes, because it affects standover height and pedaling comfort.

3. Kids’ bikes

Kids’ bikes are most often sized by wheel diameter, not frame size:

• 10″, 12″  are usually runbikes for ages under 5

• 12″, 14″, 16″ → ages ~3-6

• 20″ → ages ~6–8

• 24″ → ages ~8–10
  Once kids are tall enough, they move to adult-sized bikes.

4. Fine-tuning the fit for YOU

Even with the right frame size, bikes can be quite easily adjusted using:

• Seat height and position

• Handlebar height

• Stem length

• Saddle width

These all help dial in comfort and control. The more leisurely the ride, the more an upright riding position is appreciated, as it helps lessen pressure on the wrists, back, and neck. We will help you size the correct bike in store. The real truth comes out after riding the bike, so testing the bike on our bike trail will be very helpful in feeling the difference between models and sizes.