One of the most important steps in buying a new bike is measuring for the frame size. A bicycle that is the wrong size will be uncomfortable to ride and may even be unsafe if it is so large that you cannot control it. Riding an ill-fitted bike can also lead to knee, back or shoulder injuries. Follow these guidelines to measure for your proper bike frame size and enjoy your time out on the road in comfort.
Stand barefoot with your back against a wall. Wear your cycling clothing when measuring, especially if your shorts have extra padding in the inseam. Place a ruler or book between your legs so that it is pulled all the way up to the inside of your shorts. Mark the wall on top of the ruler or book and step away. Measure the distance in centimetres from the mark to the floor. This is your inseam measurement.
Calculate your ideal road bike size by multiplying the inseam measurement by 0.65 for bike frames that are measured centre-to-centre. If the bike frame is measured centre-to-top, multiply the inseam by 0.67.
Convert the road bike size to your ideal mountain bike size, if needed. Subtract 10 centimetres from the road bike size. Convert this measurement into inches and you will have your mountain bike frame size.
Women often have longer legs and shorter torsos than a man of the same height. Bike frames with a shorter top tube may work better for female cyclists because the handlebars are brought closer. Test out several frames at a local bike shop before making a purchase. These measurements are only a starting point to determine your exact size. Every person's body is proportioned differently, so you may need to buy a bike with a longer or shorter top tube to adjust for your arm length.