The difference between your standing reach height and the highest point you can reach when you jump vertically equals your vertical jump height. You can easily and accurately calculate your vertical jump height using chalk, a wall-mounted magnetic board or a vertical jump device.
Easy Chalk Method
Chalk the fingertips of your reaching hand and stand with your reaching arm facing a wall. Reach up and make a chalk mark on the wall to indicate your standing reach height. Now, jump as high as you can, reach up and make another chalk mark on the wall. Measure the distance between the two marks to determine your vertical jump height.
Magnetic Board Method
You can alternatively use a wall-mounted magnetic board with height markings in 1/2-inch increments and two magnets. Take one magnet, stand next to the board, reach up as high as you can while flat-footed and place the magnet on the board. Take another magnet, jump as high as you can and place the magnet on the board. Subtract the height of the lower magnet from the higher magnet to determine your vertical jump height.
Vertical Jump Device Method
This method requires a wall-mounted or freestanding vertical jump device with horizontal vanes or flags. The flags are in 1/2-inch increments and rotate out of the way when you jump. Stand below the device, reach up and adjust the device so the lowest flag touches your fingertips. Jump, touch the highest flag possible and push it out of the way. Count the number of flags you displaced and divide by two to determine your jump height in inches.