The best way to assess a person's weight and figure out his ideal weight is to determine his body mass index and waist circumference, according to the CDC. These two measurements can determine if the person is at a healthy, ideal weight or not.
Body mass index is a measurement that is calculated using a person's height and weight. If a person has a BMI of less than 18.5, he is underweight. If his BMI falls between 18.5 to 24.9, he is in the healthy weight range. If his BMI falls between 25 and 29, he is overweight; if it is above 30, he is obese.
People are also at a higher risk of developing obesity-related illnesses if their waist circumferences are above a certain threshold. Men should have a waist circumference below 40 inches, and non-pregnant women should have a waist circumference below 35 to be in a healthy range.