Age is not commonly used as a factor in determining the ideal weight of a person unless determining the ideal weights between an adult versus a child. Separate standards for ideal weights exist for children under 20, according to the Centers for Disease Control and Prevention. Body mass indexes, waist-to-hip ratios, waist-to-height ratios and body fat percentages are all methods of determining ideal weight of adults, reports Medical News Today.
Body mass indexes are calculated by dividing an individual's weight by the square of her height. This number is then used to determine if this person is overweight or underweight, according to Medical News Today. However, this method does not work with extremely muscular people, as their weight is mainly composed of muscle rather than fat.
Waist-to-hip ratios can estimate risks of developing cardiovascular issues but do not take into account body composition, reports Medical News Today. Waist-to-height ratios are indicators of diabetic risk and heart disease, with medical professionals recommending an individual's waist be less than one half her height.
Body fat percentages are possibly the most informative measurement, as it calculates how much of a person's body is strictly fat, reports Medical News Today. Medical professionals agree 18 to 25 percent fat is an acceptable range for males and 25 to 31 percent an acceptable range for females.