BMI Calculator
BMI is a rough screening number, not a diagnosis. It is useful for spotting a trend and useless for telling a muscular person anything at all.
How the math works
BMI = 703 x weight in pounds / (height in inches)^2. The 703 converts the original metric formula, weight in kilograms over height in meters squared. The healthy weight range is that formula solved backwards at BMI 18.5 and 24.9.
Common questions
- What is a healthy BMI?
- The standard adult ranges are under 18.5 underweight, 18.5 to 24.9 healthy, 25 to 29.9 overweight and 30 or above obese. They are population averages and were never meant to judge an individual on their own.
- Is BMI accurate?
- For a large group, yes. For one person, only loosely. It uses no information about muscle, bone or where fat sits, so a lifter and a sedentary person of the same weight get the same number. Waist measurement adds more than BMI does.
- Does BMI work for children or older adults?
- Not with these ranges. Children use age and sex percentile charts, and in older adults a slightly higher BMI is often associated with better outcomes. Both cases need a doctor rather than a formula.