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How to Determine the Correct Frame Size for a Bike

When purchasing a new bicycle, be sure to take measurements and get the right fit. Just a push -- and a few numbers -- and you're on the way!


  • Step 1: Measure your inseam Measure your inseam by standing barefoot with your back against a wall, looking straight ahead. Hold an inch-thick book between your legs. Measure the distance in centimeters from the top edge of the book to the floor.
  • TIP: Perform the measurement three or four times and calculate the average.
  • Step 2: Find your C-C size Determine your measurement for a center-to-center measured road bike frame, which measures from the center of the bottom bracket to the center of the top tube, by multiplying your inseam by .65.
  • Step 3: Find your C-T size Figure your measurement for a center-to-top measured road bike frame, which measures from the center of the bottom bracket to the top of the top tube or seat lug, by multiplying your inseam by .67. This accounts for the additional length of the top of the seat tube.
  • Step 4: Find your mountain bike size Adjust your measurement by subtracting 10 to 12 centimeters from your center-to-top road bike size and converting it to inches to determine your center-to-top mountain bike size.
  • TIP: Convert centimeters to inches by multiplying by .3937.
  • Step 5: Consider your body type Since women generally have longer legs and shorter torsos than men, women should look for frames with shorter top tubes or frames that are specially made for women. Men with shorter upper bodies or who prefer a more upright position should also consider frames with shorter top tubes.
  • Step 6: Consider your limb proportions Divide your height by your inseam if you have unusually long or short limbs. If the quotient is more than 2.2, you will need a longer reach or top tube. If it is less than 2.2, you will need a shorter reach or top tube.
  • Step 7: Take test rides Test ride several different frame sizes, taking into account any top tube length added by the saddle post, to get a clearer idea of the size most comfortable for you.
  • FACT: Of the 60 riders participating in the first Tour de France in 1903, only 21 finished the race.

You Will Need

  • Wall
  • Book
  • Measuring tape
  • Calculator
  • Body type knowledge
  • Test rides

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