Body Mass Index (BMI) is a quick screening measure that relates your weight to your height. It doesn’t measure body fat directly, but it’s a useful, well-studied starting point for understanding weight-related health risk at a population level.
Body mass index against the WHO reference ranges.
Anyone who wants a fast, standardized read on their weight relative to height — most useful as a starting point before looking at body composition measures like body fat percentage or waist-to-height ratio.
BMI is calculated as weight in kilograms divided by height in metres squared (kg/m²). The World Health Organization defines under 18.5 as underweight, 18.5–24.9 as healthy weight, 25–29.9 as overweight, and 30+ as obesity. These thresholds were derived from population studies linking BMI to mortality and disease risk, but they don’t adjust for muscle mass, bone density, age or ethnicity — a muscular athlete can register as “overweight” despite low body fat.
Not reliably. BMI can’t distinguish muscle from fat, so muscular or highly athletic people often score higher than their actual body-fat level would suggest. Body Fat % or Lean Body Mass are better measures in that case.
The WHO healthy range is 18.5–24.9 for most adults. It’s a population-level guideline, not an individual diagnosis — your clinician will weigh it alongside other factors.
The standard adult BMI formula and thresholds are the same for men and women and for most adults, though clinical interpretation often adjusts for age, ethnicity and muscle mass.
These calculators provide general wellness estimates based on established formulas and are not a substitute for professional medical advice, diagnosis or treatment. If you have a medical condition or are pregnant, consult a qualified healthcare provider before making changes based on these results.