BMI Calculator (Body Mass Index)

What is Body Mass Index (BMI)?

Body Mass Index (BMI) is a numerical value calculated from a person’s weight and height. It is widely used as a screening tool to assess whether an individual has a healthy body weight in relation to their height.

BMI is recommended by the World Health Organization (WHO) as a standard method for identifying underweight, overweight, and obesity in adults.

How is BMI calculated?

The formula used to calculate Body Mass Index is:

BMI = weight (kg) / [height (m)]²

For example, a person who weighs 70 kilograms and is 1.70 meters tall will have a BMI of approximately 24.2.

BMI categories for adults

• Underweight: BMI below 18.5
• Normal weight: BMI between 18.5 and 24.9
• Overweight: BMI between 25 and 29.9
• Obesity: BMI 30 or higher

These BMI ranges apply to adults aged 20 years and older, regardless of gender.

BMI for children and teenagers

For children and adolescents under the age of 20, BMI is interpreted differently than for adults. Instead of fixed ranges, BMI values are compared against age- and sex-specific percentile charts.

This BMI calculator uses real medical BMI percentile tables for children and teenagers, ensuring an accurate and age-appropriate interpretation.

Differences between men and women

While the BMI formula is the same for both men and women, body composition differs between sexes. Men generally have more muscle mass, while women tend to have a higher percentage of body fat.

Because of this, BMI should always be interpreted alongside other health indicators such as age, lifestyle, and overall body composition.

Limitations of BMI

• BMI does not distinguish between muscle and fat mass
• It may overestimate body fat in muscular individuals
• It does not account for fat distribution
• It should not be used as a sole diagnostic tool

For a complete health assessment, BMI should be combined with other measurements such as waist circumference, body fat percentage, and medical evaluation.