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Did you find a bicycle at a garage sale or on craigslist but don’t know its size? We’ll show you how to measure a bicycle frame to determine its size.
Bicycles are sold by frame height, and that is the primary measurement that determines if a bike fits the rider or not. The main purpose of this article is to show how to measure a bike frame. If you need to find out if a particular bicycle frame fits you, see my article about road bike sizing.
How to Measure a Bicycle Frame
Frame size is measured from the center of the bottom bracket at the crank spindle to the top of the seat tube where the seat post enters the frame.
Hold the end of your tape measure at the center of the bottom bracket spindle and measure to the top of the seat tube.
Use the table below if you need to convert your measurement from inches to centimeters or from centimeters to inches.
| Frame Size | |
|---|---|
| Inches | Centimeters |
| 16.0 | 40.6 |
| 16.5 | 41.9 |
| 17.0 | 43.2 |
| 17.5 | 44.5 |
| 18.0 | 45.7 |
| 18.5 | 47.0 |
| 19.0 | 48.3 |
| 19.5 | 49.5 |
| 20.0 | 50.8 |
| 20.5 | 52.1 |
| 21.0 | 53.3 |
| 21.5 | 54.6 |
| 22.0 | 55.9 |
| 22.5 | 57.2 |
| 23.0 | 58.4 |
| 23.5 | 59.7 |
| 24.0 | 61.0 |
| 24.5 | 62.2 |
| 25.0 | 63.5 |
| 25.5 | 64.8 |
| 26.0 | 66.0 |
| 26.5 | 67.3 |
| 27.0 | 68.6 |
| 27.5 | 69.9 |
| 28.0 | 71.1 |
That’s all there is to measuring a bicycle frame to determine its size. There are other frame measurements, but frame height is the most important measurement as far as frame fit for a particular rider is concerned.
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The initial diagram is misleading. It`s showing the distance A as vertical instead of along the length of the tube. The two will be different. I assume from the pictures that you measure along the tube not the vertical height from the crank to the top of the tube?
You are correct. The measurement is taken along the length of the tube. The two photos in the article show illustrate how to measure a bicycle frame better than the diagram at the top of the article does.