BMI is a generalisation. Then, it depends on your built, on the composition of your body. A much better measurement is your fat percentage, because that is much more personal. A woman's body should have a minimum of 6% body fat, which is essential for the body's survival. up to 12-15% is athlete, 15% to 25% is normal from what I remember, and then there was the obese and morbidly obese. You need a precision instrument used by doctors and dietologists to measure precisely your body fat, but you can find out roughly your level through fat measurement scales and other tools.