A Common Sense Guide to Bicycles

How to Measure a Hardtail Mountain Bike

Most mountain bikes today are hardtails, meaning they have suspension in the front, not in the rear. This style is common among mid-level and high end bikes. They are usually made from steel, aluminum or carbon fiber, accommodate 26" or 29" tires, and have flat handle bars with trigger or grip-type shifters. The frame size is determined by the length of the seat tube. The instructions below explain how to measure a hardtail mountain bike.

Hardtail mountain bike

Hardtail Mountain Bike

Rider Charts

Once you know your bike's frame size, select it from the drop-down to see how tall riders should be to use this bike.


Center to Top (C-T) - This is the length of the seat tube, measured from the center of bottom bracket to top of the seat tube.

US (in) - Mountain bikes are measured in inches.

Frame Diagram

Hardtail mountain bike frame with seat tube measurement highlighted

Measuring Instructions

  1. Identify the top of the seat tube, where the seat clamp holds the seat post.
  2. Identify the center of the bottom bracket (it's the axle that holds the crank arms together).
  3. Measure the distance between the two points (C-T) - this is the length of the seat tube.
  4. Record your measurement in both centimeters (cm) and inches (to the nearest half-inch).
  5. Select your bike size from the drop-down on the right to see a rider height chart.