How to use
- Choose Metric or Imperial. Stones work too.
- Enter your weight and height.
- See your BMI, your category and the healthy weight range for your height.
BMI formula
BMI = weight (kg) ÷ height (m)²
In pounds and inches, BMI = 703 × weight (lb) ÷ height (in)². We use the exact factor of about 703.07, so imperial and metric results match.
Examples
- 70 kg, 175 cm: 70 ÷ 1.75² = 22.9, a healthy weight
- 200 lb, 5 ft 8 in: 703.07 × 200 ÷ 68² ≈ 30.4, obesity class 1 (the CDC’s own example)
Adult BMI categories
| Category | Standard | Lower thresholds |
|---|---|---|
| Underweight | Below 18.5 | Below 18.5 |
| Healthy weight | 18.5 to 24.9 | 18.5 to 22.9 |
| Overweight | 25 to 29.9 | 23 to 27.4 |
| Obesity class 1 | 30 to 34.9 | 27.5 to 32.4 |
| Obesity class 2 | 35 to 39.9 | 32.5 to 37.4 |
| Obesity class 3 | 40 or more | 37.5 or more |
The lower thresholds are for many people of Asian, Middle Eastern, Black African or African-Caribbean background, whose health risks start at a lower BMI (WHO 2004, NICE).
Healthy weight by height
| Height | Healthy weight (kg) | Healthy weight (lb) |
|---|---|---|
| 150 cm (4 ft 11 in) | 41.6 – 56.1 | 91.6 – 123.7 |
| 160 cm (5 ft 3 in) | 47.3 – 63.8 | 104.2 – 140.8 |
| 170 cm (5 ft 7 in) | 53.4 – 72.1 | 117.6 – 158.9 |
| 175 cm (5 ft 9 in) | 56.6 – 76.4 | 124.6 – 168.4 |
| 180 cm (5 ft 11 in) | 59.8 – 80.8 | 131.8 – 178.2 |
| 190 cm (6 ft 3 in) | 66.7 – 90.0 | 146.9 – 198.5 |
Limits of BMI
- It can’t tell muscle from fat.
- It is not for children, teenagers or pregnancy.
- At the same BMI, women and older adults tend to carry more body fat.
A doctor may also look at waist size, blood pressure and blood tests.
Need to convert your height first? Use the length converter.