Calculator
How it works and when to use it
Body mass index is your weight in kilograms divided by the square of your height in metres, and WHO classes adults as: under 18.5 underweight, 18.5 to 24.9 normal weight, 25 to 29.9 overweight, and 30 or more obesity.
The calculator also shows the weight range that gives a normal BMI for your height.
Reference: BMI = weight (kg) / height (m)²; WHO Technical Report Series 894, Obesity (2000); under 18: BMI-for-age charts (WHO 2006/2007)
Frequently asked questions
Can BMI be used for children?
Not with the adult classes under 18, it is read on growth charts by age and sex, and the paediatrician assesses it.
What are its limits?
It does not tell fat from muscle, so it can be high in athletes without extra fat, and a waist measurement helps estimate belly fat.
Can it be used in pregnancy?
No, during pregnancy BMI is taken from the weight before pregnancy to set the right weight gain, which your obstetrician follows.
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Clinic software for this specialty
Try Clinicato for your clinic
These calculators are free here for everyone, and in Clinicato 49 medical tools work inside the patient's file with the "Medical tools" add-on: filled from the visit and the vital signs, with the result added to the visit's plan, next to appointments, prescriptions and invoices.