BMI Calculator
Calculate your Body Mass Index per WHO standards.
Online BMI calculator: know your body mass index
The Body Mass Index (BMI) is a measurement developed by Belgian mathematician Adolphe Quetelet in the 19th century and adopted by the World Health Organization (WHO) as a body weight classification tool. It is calculated by dividing weight in kilograms by height in meters squared (kg/m²). The WHO establishes the following categories: underweight (less than 18.5), normal weight (18.5 to 24.9), overweight (25 to 29.9), and obesity in three degrees (30 or more).
Although BMI is a useful tool for quickly assessing body weight at the population level, it has important limitations at the individual level. It does not distinguish between muscle mass and body fat, does not consider fat distribution, and does not account for factors such as age, sex, ethnicity, or body composition.
Our calculator supports both the metric system (kilograms and centimeters) and imperial (pounds and inches), and shows the classification according to WHO categories with intuitive color codes. Remember that BMI is only a guideline and does not replace evaluation by a health professional.
Frequently asked questions
Is BMI accurate for everyone?
No, BMI has significant limitations for certain groups. It is not reliable for athletes and people with high muscle mass, pregnant women, people over 65 (who naturally lose muscle mass), or children and adolescents (who require age-specific percentile charts). For a more complete assessment, it is recommended to complement with waist circumference measurements and body fat percentage.
What BMI is healthy?
According to the WHO, a BMI between 18.5 and 24.9 is considered normal and healthy weight for most adults. However, the "ideal" range may vary depending on age, sex, and ethnicity. Some studies suggest that a slightly higher BMI (up to 27) in older adults may be associated with better survival, while for Asian populations the overweight threshold may be lower.
Does BMI consider muscle mass?
No, BMI only uses total weight and height without distinguishing between muscle mass, fat, bone, and water. A person with a lot of muscle mass can have a high BMI without having excess fat. That is why, for a more precise assessment of body composition, complementary methods such as bioelectrical impedance analysis, DEXA absorptiometry, or skinfold measurements are recommended.
Want to learn more? Read our complete guide →