How to Determine Frame Size on a Bicycle

Proper bicycle fit is important for safety and comfort.

A bicycle needs to fit like a pair of shoes. If it doesn't fit properly it can cause discomfort or danger, and most importantly, it won't be any fun. Here are a few easy steps to ensure that your road or mountain bike fits like, well, a bike.

Things You'll Need

• Tape measure
• Book
• Pencil
• Calculator

Instructions

1. Stand barefoot with your back against the wall and your feet roughly 6 inches apart.

2. Place the book between your legs and press it firmly into your crotch--simulating a bike seat.

3. Have a friend (a close friend would be best) measure the distance between the top of the book (your crotch area) and the floor. If you're alone, mark the wall with a pencil at the top of the book and measure the distance between the mark and the floor. You want centimeters, not inches. We'll convert to inches in the next step. This number is your inseam measurement.

4. Multiply your inseam by 0.65 cm. That's your road bike frame size in centimeters. Divide by 2.54 to convert to inches. For example 80 cm (inseam) x 0.65 = 52 cm; 52/2.54 = 20.5 inches. So you would need a road bike with a 20- or 21-inch frame.

   For a mountain bike, multiply your inseam by 0.59 then divide by 2.54 to convert to inches.

Tips & Warnings

• These measurements are not an exact science and do not account for personal preference. The best way to get the right measurement would be to test-ride a bunch of bikes at the shop and see what feels best.

References

• How to Measure for a Road Bike Fit