Learn about plyometrics. Plyometrics are exercises that use the resistance of your own body to build strength and are essential for building the kind of strength necessary to build your jump. It takes time to train your body to jump higher, but working the right muscle groups can improve your explosiveness and height without maxing out regularly in the weight room.
The method described above is the most common and simplest way to measure one's vertical jump, but other more scientifically accurate methods have been devised. A pressure pad can be used to measure the time it takes for an athlete to complete a jump, and then using a kinematics equation (h = g × t2/8), the computer can calculate his or her vertical jump based on the time in the air.