BMI and What It Actually Tells You (and What It Doesn't)
BMI is the most common health screening number — but it has real limitations. Here is how to interpret it correctly and what to measure alongside it.
What BMI measures
Body Mass Index is your weight in kilograms divided by your height in meters squared. It sorts adults into ranges: under 18.5 (underweight), 18.5–24.9 (normal), 25–29.9 (overweight), and 30+ (obese). It is fast, free, and useful at a population level.
Where BMI falls short
- It cannot distinguish muscle from fat — many athletes register as "overweight".
- It ignores where fat is stored; abdominal fat carries more health risk.
- It is less accurate for older adults, pregnant people, and some ethnic groups.
What to measure alongside it
Pair BMI with waist circumference and, if possible, body fat percentage for a fuller picture. Trends over time matter more than a single reading. Use our BMI, Body Fat, and Ideal Weight calculators together, and treat the numbers as a conversation starter with a healthcare provider — not a diagnosis.
Try the calculators
BMI Calculator
Calculate your Body Mass Index (BMI) and find out what it means for your health.
Body Fat Percentage Calculator
Estimate your body fat percentage using the Navy method.
Ideal Weight Calculator
Find your ideal body weight range based on height and frame size.
Calorie Calculator
Calculate your daily calorie needs based on age, weight, height, and activity level.