How BMI is calculated
BMI uses your weight and height with this formula:
For imperial units the calculator converts feet/inches and pounds to metric first, then applies the same formula, so the result is identical either way.
What your result means
- Under 18.5 — Underweight
- 18.5 – 24.9 — Normal weight
- 25 – 29.9 — Overweight
- 30 and above — Obese
The "healthy weight range" shown is the span of weights that would place you in the normal-BMI band for your current height.
Frequently asked questions
What is BMI?
Body Mass Index (BMI) is a simple ratio of weight to height (kg ÷ m²). It is a quick screening tool to estimate whether a person is underweight, normal weight, overweight, or obese.
What are the BMI categories?
For adults: below 18.5 is underweight, 18.5–24.9 is normal weight, 25–29.9 is overweight, and 30 or above is obese.
Is BMI accurate for everyone?
BMI does not distinguish muscle from fat, so it can misclassify very muscular people, and it is interpreted differently for children, pregnant women and the elderly. Use it as a general guide, not a diagnosis.
How do I lower my BMI?
BMI falls when weight decreases relative to height, generally through a sustainable combination of balanced nutrition and regular physical activity. Consult a healthcare professional for personalised advice.
For general information only — not medical advice.