BMI calculator
Your body mass index, what category it falls in, and the healthy weight range for your height.
How it’s worked out
- Height
- Weight
- BMI
- BMI = kg ÷ m²
- Healthy range
BMI categories for adults
| Category | BMI | Weight at your height |
|---|
What BMI can and can’t tell you
BMI is a quick screening number that compares weight with height. Across large groups it tracks body fat and health risk reasonably well, which is why doctors use it as a starting point. For one person it is a rough guide: it doesn’t separate muscle from fat or see where fat is stored. Children and teens are assessed with age-based percentiles instead.
Questions people ask
What is a healthy BMI?
For adults, a BMI from 18.5 to 24.9 is classed as a healthy weight by the World Health Organization. Below 18.5 is underweight, 25 to 29.9 is overweight, and 30 or more is obesity, split into classes I (30–34.9), II (35–39.9) and III (40 and over).
How is BMI calculated?
BMI is weight in kilograms divided by height in meters squared. In US units it is 703 × weight in pounds ÷ height in inches squared.
Is BMI accurate for athletes?
Not always. BMI can’t tell muscle from fat, so muscular people can be classed as overweight while carrying little fat. Waist measurement and body fat percentage add useful context.