BMI Calculator

Simple, fast and easy

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Calculate BMI for children and adolescents (5 to 19 years)

Result

Result: Fill in the fields
Classification: Fill in the fields
Ideal weight: Fill in the fields

See also:

Classification table How BMI is calculated Fun facts about BMI

How BMI is calculated

Expression:

$$\text{IMC} = \frac{\text{peso }}{\text{altura}^2}$$

Where:

Variable Unit of measurement Symbol
BMI Kilograms per square meter Kg/m2
weight Kilograms Kg
height Meter m

BMI Classification Table for adults

# Classification BMI (kg/m²) Description
1 Underweight Less than 18.5 Insufficient body weight for height. Increased risk of health problems.
2 Normal weight 18.5 to 24.9 Adequate weight for height. Low risk of weight-related health problems.
3 Overweight 25,0 a 29,9 Excess weight for height. Moderate increased risk of chronic diseases.
4 Obesity Grade I 30,0 a 34,9 Mild obesity. High risk of diseases such as diabetes, hypertension, and cardiovascular diseases.
5 Obesity Grade II 35,0 a 39,9 Moderate obesity. Very high risk of chronic diseases and complications.
6 Obesity Grade III Greater than or equal to 40.0 Severe or morbid obesity. Extremely high risk of serious diseases and reduced life expectancy.

Note that, if the BMI value is, for example 24.95, it will be considered 'Normal weight', since overweight starts from a BMI of 25.00.

Fun facts about BMI

  • BMI was created in 1832 by Adolphe Quetelet, a Belgian astronomer and mathematician.
  • Originally, it was not intended for individual diagnosis, but for population studies.
  • The World Health Organization (WHO) adopted BMI as a global standard in 1995.
  • Used in medical check-ups, scientific research, and even life insurance.
  • Assists in the early detection of health risks such as diabetes and heart diseases.
  • Fundamental for epidemiological analysis and public health planning.
  • Does not differentiate muscle mass from body fat.
  • May underestimate risks in people with abdominal fat.
  • Less effective for children, the elderly, and high-performance athletes.
  • Small changes in height strongly impact BMI.
  • Alternatives like WHR (waist-hip ratio) assess fat distribution.
  • Exams like bioimpedance and DEXA provide more accurate body analysis.
  • Studies show that BMI outside the ideal range is associated with lower longevity.
  • A person can have a normal BMI but be metabolically unhealthy — the famous “skinny fat”.
  • BMI is just one of the factors used for general health assessment.