Body Mass Index (BMI) is the screening tool doctors and health organizations worldwide use to classify weight relative to height. It doesn't measure body fat directly, but decades of population data link BMI ranges to health risk, which makes it a fast, free first check — enter your height and weight and get your number and category instantly.
Cómo funciona
The calculator divides your weight in kilograms by the square of your height in meters, then maps the result onto the World Health Organization's standard adult categories: under 18.5 is underweight, 18.5–24.9 normal, 25–29.9 overweight, and 30 or above obese.
La fórmula
Weight in kilograms, height converted from centimeters to meters before squaring. The same formula applies to men and women; separate growth-chart percentiles are used for children.
Ejemplo resuelto
At 170 cm and 70 kg: BMI = 70 ÷ (1.70)² = 70 ÷ 2.89 ≈ 24.2, which lands in the normal range — near its upper edge, so a few kilograms of gain would cross into overweight.
Preguntas frecuentes
Is BMI accurate for athletes?
Often not. Muscle is denser than fat, so muscular people can read as overweight while carrying little fat. For athletic builds, pair BMI with a body-fat estimate or waist measurement for a fuller picture.
Do BMI categories differ by region?
The WHO thresholds above are the global standard, but several Asian health authorities use lower cut-offs (e.g., overweight from 23) because health risks appear at lower BMI in some populations.
Does BMI apply to children?
Not with adult cut-offs. Children's BMI is assessed against age- and sex-specific percentile charts, since healthy body composition changes throughout growth.
BMI is a screening indicator, not a diagnosis. For personal health decisions, consult a qualified healthcare professional.