How the bmi calculator works
BMI is a simple screening measure that relates body weight to height:
BMI = weight (kg) ÷ height (m)²
For imperial units: BMI = 703 × weight (lb) ÷ height (in)²
| BMI range | Category |
|---|---|
| Below 18.5 | Underweight |
| 18.5 – 24.9 | Normal weight |
| 25.0 – 29.9 | Overweight |
| 30.0 and above | Obese |
Step-by-step guide
- Choose metric or imperial units.
- Enter your height.
- Enter your current weight.
- Read your BMI, category, and the healthy weight range for your height.
Why BMI has limitations
Because BMI uses only height and weight, two people with the same BMI can have very different body compositions — one with more muscle, one with more fat. It remains widely used because it's simple, free, and correlates reasonably well with health risk at a population level, but it shouldn't replace a fuller clinical assessment.
Frequently asked questions
BMI is a useful population-level screening tool, but it doesn't distinguish muscle from fat. It can overestimate body fat in muscular individuals and underestimate it in older adults who've lost muscle mass. It's also not designed for children, pregnant women, or elite athletes.
The WHO defines 18.5–24.9 as the normal weight range for most adults, though healthy ranges can vary somewhat by ethnicity and individual body composition.
No. BMI is a starting point, not a diagnosis. Talk to a healthcare provider who can consider waist circumference, body composition, and your overall health picture.