How to Size a Road Bike

1. Choose the frame type. Choose a C-C or C-T frame.
2. 2
   Measure your inseam.

   • Stand with your back against a wall.
     
   • Place your feet 6 to 8 inches (15 to 20 cm) apart.
     
   • Stand a book upright between your legs. The spine of the book should face away from the wall. The other edge of the book should touch the wall.
     
   • Lift the book to your crotch. You should feel as if you are seated on a bicycle saddle.
     
   • Get an assistant to measure the distance between the top of the book and the ground. This is your inseam.
     
3. 3
   Calculate the frame size.

   • Multiply your inseam measurement by .65 if you have a C-C frame. If your inseam measurement is 30 inches (76.2 cm), the result is 19.5 inches (49.5 cm). Your frame should be as near to 19.5 inches (49.5 cm) as possible.
     
   • Multiple your inseam measurement by .67 if you have a C-T frame. If your inseam measurement is 30 inches (76.2 cm), the result is 20.1 inches (51.1 cm). Your frame should be as near to 20.1 inches (51.1 cm) as possible.
     
4. 4
   Calculate total reach. Total reach indicates how far you should stretch horizontally over the bike from the seat to the handlebars. A measurement of total reach denotes the distance from one end of the top stem, or crossbar, to the tube where the handlebars attach to the bike.

   • Stand with your back against a wall.
     
   • Hold a pencil. Make a fist around the pencil.
     
   • Hold your arm straight out at your side. Your arm should be parallel to the ground.
     
   • Get an assistant to use a tape measure to determine the length between the point on your collarbone nearest to your shoulder and the pencil. This is your arm length.
     
   • Stand a book upright between your legs. The spine of the book should face away from the wall. The other edge of the book should touch the wall.
     
   • Lift the book to your crotch.
     
   • Get an assistant to use a tape measure to determine the length between the top of the book and the hollow in your neck, just below the Adam's apple. This is your torso length.
     
   • Add arm length to torso length. An arm length of 24 inches (61 cm) and a torso length of 24 inches (61 cm) will give you a total of 48 inches (122 cm).
     
   • Divide the total by 2. A total of 48 inches (122 cm) gives you 24 inches (61 cm).
     
   • Add 4 inches (10.2 cm) to that number. You now have 28 inches (71.2 cm). From one end of the top stem to the tube where the handlebars attach to the frame, your bike should measure as close to 28 inches (71.2 cm) as possible.