What your BMI really means (and its blind spots)

BMI (Body Mass Index) is the world's most used health screening number — and the most misunderstood. Here's how to read it honestly.

The categories

Under 18.5 underweight · 18.5–24.9 normal weight · 25–29.9 overweight · 30+ obese. These cut-offs come from the WHO and are population-level tools, not personal verdicts.

The blind spots

BMI can't tell muscle from fat. A very muscular athlete can show 'overweight' while being extremely lean, and BMI says nothing about where fat sits — abdominal fat is riskier than fat elsewhere.

Use it as a starting point

Combine BMI with waist circumference and, most importantly, your doctor's advice. Check your number now with our free BMI calculator.