A Common Sense Guide to Bicycles

How to Measure a Racing BMX Bike

Racing BMX bikes are built for fast riding on dirt tracks with big jumps and high banking turns. The frame is strong, lightweight, made from steel or aluminum, with a compact design and gearing that allows higher top end speeds. Most racing BMX bikes use 20" tires and cruiser class frames use 24" tires. The frame size is determined using the top tube length. The instructions below explain how to measure a racing BMX bike.

Racing BMX bike

Racing BMX 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.


Top Tube Length (TT) - This is the length of the top tube, measured from the center of the seat tube to center of the head tube.

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

Frame Diagram

Racing BMX frame with top tube measurement highlighted

Measuring Instructions

  1. Identify intersection of the top tube and seat tube.
  2. Identify the intersection of the top tube and head tube.
  3. Measure the distance between these two points (TT) - this is the length of the top 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.