A Common Sense Guide to Bicycles

How to Measure a Traditional Mountain Bike

Traditional mountain bikes, those without suspension, are common among older used bikes. They are usually made from steel or aluminum, accommodate knobby 26" tires, and have flat handlebars with trigger or grip-type gear shifters. The frame size is determined by the length of the seat tube. The instructions below explain how to measure a traditional mountain bike.

Traditional mountain bike

Traditional 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

Traditional 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.