Measure body weight using a scale
Measure height using a stadiometer or tape measure
Use the body mass index formula: BMI = weight in kilograms ÷ height in meters squared
Convert weight to kilograms if needed
Convert height to meters if needed
Square the height value
Divide the weight by the squared height
Record the result as body mass index if that is the intended measure
Use direct weighing if you need body mass in kilograms only