How to use
Choose US units (feet, inches and pounds) or metric (centimeters and kilograms), then enter your height and weight. You get:
- Your BMI and adult weight category.
- Healthy weight for your height: the weights that give a BMI of 18.5 to under 25.
- To reach a healthy weight: how many pounds or kilograms to lose or gain to get into that range.
Waist size is optional. Pick your sex and enter your waist to check for extra fat around the middle. Measure standing up, just above your hipbones, after breathing out normally.
How BMI is calculated
BMI = weight (kg) ÷ height (m)²
BMI = 703 × weight (lb) ÷ height (in)²
Adult BMI categories used by the CDC and WHO:
| BMI | Category |
|---|---|
| Below 18.5 | Underweight |
| 18.5 to under 25 | Healthy weight |
| 25 to under 30 | Overweight |
| 30 to under 35 | Obesity class 1 |
| 35 to under 40 | Obesity class 2 |
| 40 or higher | Obesity class 3 (severe obesity) |
Waist size: more than 40 inches (102 cm) for men or more than 35 inches (88 cm) for women increases the risk of heart disease and type 2 diabetes.
Examples
| Height | Weight | BMI | Category | Healthy weight range |
|---|---|---|---|---|
| 5 ft 9 in | 160 lb | 23.6 | Healthy weight | 126–169 lb |
| 5 ft 4 in | 180 lb | 30.8 | Obesity class 1 | 108–145 lb (lose 35 lb) |
| 6 ft 0 in | 150 lb | 20.3 | Healthy weight | 137–184 lb |
For the first row: 5 ft 9 in is 69 inches, so 703 × 160 ÷ 69² = 23.6.
Keep in mind
BMI is a quick screening tool, not a diagnosis. It doesn’t measure body fat directly, and the same BMI can mean different health risks depending on muscle mass, age, sex and ethnicity. Talk to your doctor before making decisions about your weight or health.