Tools
BMI calculator
Your body mass index, its WHO category and the weight range that counts as normal for your height.
Fill in the fields to see your result.
How it is calculated
BMI is your weight in kilograms divided by your height in metres squared: 80 kg at 1.80 m gives 80 ÷ (1.8 × 1.8) = 24.7. The categories are the World Health Organization’s for adults.
BMI only knows height and weight, so it cannot tell muscle from fat. A muscular athlete can come out as overweight while lean. It is not used for children and teenagers, who are rated against growth charts for their age.
BMI categories
| Category | BMI |
|---|---|
| Underweight | < 18.5 |
| Normal weight | 18.5–24.9 |
| Overweight | 25–29.9 |
| Obesity class I | 30–34.9 |
| Obesity class II | 35–39.9 |
| Obesity class III | ≥ 40 |
Source: World Health Organization, adults 18 and over.
Questions
What is a healthy BMI?
- For adults the World Health Organization puts normal weight at a BMI of 18.5 to 24.9. 25 to 29.9 counts as overweight and 30 or more as obesity.
Is BMI accurate for athletes?
- Not always. BMI uses only height and weight, so a muscular athlete with little body fat can come out as overweight. Body fat percentage or the fat-free mass index (FFMI) says more about them.
How do you calculate BMI?
- Divide your weight in kilograms by your height in metres squared. For 80 kg and 1.80 m: 80 ÷ 3.24 = 24.7.
Tviky gives general training information, not medical advice. If you are injured or in pain, see a physiotherapist before training.