The BMI Formula
The BMI uses an simple formula that is non-sex specific--use the same formula for both men and women. Use the following equation to calculate your BMI using pounds and inches:

Interpreting the Results
Meaning (Quetelet 1989):

BMI Meaning
less than 19.9 Underweight
20.0 to 24.9 Normal weight
25 to 29.9 Obesity level 1
30 to 39.9 Obesity level 2
40 or more Obesity level 3 or morbid obesity

Age BMI     Normal weight

19–24               19–24
25–34               20–25
35–44               21–26
45–54               22–27
55–64               23–28
Ab 65                24–29
 

Keep in mind that the BMI is a general classification of body mass that is non-specific to sex, age and other factors such as your physical activity. For a more accurate assessment of obesity, there are a number of other tests like skinfold thickness, underwater weighing or other laboratory procedures.