Body Mass Index (BMI) is a single number calculated from your height and weight. It is used around the world as a first-pass screening tool for weight-related health risk.
The ranges
- Below 18.5 — Underweight
- 18.5 to 24.9 — Healthy weight
- 25 to 29.9 — Overweight
- 30 and above — Obese
What BMI gets wrong
BMI cannot tell muscle from fat. A very muscular rugby player often has a BMI above 30 but very low body fat. Conversely, people with low muscle mass may have a "normal" BMI and carry unhealthy amounts of visceral fat — a phenomenon sometimes called skinny fat.
Use it alongside other measures
Waist-to-hip ratio, waist circumference, body-fat percentage and routine blood tests paint a much fuller picture. See our BMI calculator for your number — then take it to a conversation with your doctor.