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# How To Determine Bike Frame Size

By: Daniel Parrish

Break Studios Contributing Writer

So, you're thinking about buying a new bike and you need to know how to determine the bike frame size? You should aim to buy a bike with the correct frame size for you, because if you don't, riding your bike will be uncomfortable, thus making you less able to ride long distances. Here is how you determine the size of your bike frame.

1. Measure your inseam. First, find a book and a pencil. Now, stand up against a wall and put the book in between your legs so that it will press up against your pelvic bone. Take the pencil and make a mark on the wall along the top of the book. Now, take a ruler and measure from the mark down to the floor. Also, make sure that you measure in centimeters! Make sure to measure multiple times to make sure that your measurements are accurate.
2. Getting the bike frame size in inches. Using your inseam measurement will help you determine your bike frame size. Take your inseam measurement and multiply it by 0.65. Now, take the result and convert it to inches by dividing it by 2.54. The result should now be your bike frame size in inches! For example, if your inseam measurement was 85 centimeters, take that and multiply it by 0.65. You'd get 55.25. Then, take 55.25 and divide it by 2.54. You'll get about 21.75, so the size of your bike frame will be 21.75" or 22".
3. Getting the bike frame size in centimeters. This is similar to determining the bike frame size in inches, but with one step fewer. Take your inseam measurement and multiply it by 0.65. The result will be your bike frame size in centimeters. So, if your inseam measurement was 85 centimeters, your bike frame size would be 55.25 centimeters, because 85 multiplied by 0.65 is 55.25.
4. Take a bike out for a test ride. Test a bike that has your determined size of bike frame. Chances are it'll feel pretty comfortable to you. If it's not comfortable at all and it's the wrong size, then you may have made an error in measurement. Go back and re-measure your inseam and do all of the math again.
Posted on: Sep. 26, 2010