BMI Calculator (Body Mass Index)
Enter your weight and height to instantly calculate your BMI and find out your weight category.
What is BMI?
Body Mass Index (BMI) is a simple indicator that relates a person's weight to their height to estimate whether they fall within a range considered healthy. It's used by healthcare professionals worldwide as a first reference point, but it does not replace a full medical assessment: it doesn't account for muscle mass, age, sex, or fat distribution.
How is BMI calculated?
The BMI formula is: weight (in kilograms) divided by height (in meters) squared.
BMI = weight (kg) / [height (m)]²
For example, a person weighing 70 kg and measuring 1.75 m has a BMI of 70 / (1.75 × 1.75) ≈ 22.9, which falls into the normal weight category.
BMI categories
- Below 18.5: Underweight
- 18.5 to 24.9: Normal weight
- 25 to 29.9: Overweight
- 30 and above: Obese
These thresholds are set by the World Health Organization (WHO) for the general adult population.
Frequently asked questions
Is BMI reliable for athletes?
Not always. A very muscular person can have a high BMI without excess body fat, since muscle is denser than fat. BMI remains a general indicator, not a precise measure of body composition.
Is BMI calculated the same way for children?
The formula is the same, but the result is interpreted differently using growth charts specific to age and sex.
What if my BMI is outside the normal range?
This result is informational and does not replace advice from a healthcare professional. Consult a doctor for any questions about your weight or health.