Calc Function

    • Calcs that help predict probability of a diseaseDiagnosis
    • Subcategory of 'Diagnosis' designed to be very sensitiveRule Out
    • Disease is diagnosed: prognosticate to guide treatmentPrognosis
    • Numerical inputs and outputsFormula
    • Med treatment and moreTreatment
    • Suggested protocolsAlgorithm





    Chief Complaint


    Organ System


    Patent Pending

    Log in to create a list of your favorite calculators!

    Body Mass Index (BMI) and Body Surface Area (BSA)

    Calculates body mass index and body surface area.
    Why Use
    The BMI has been criticized for being an inappropriate measure for very muscular individuals who are in excellent physical condition, and also being inappropriate in some ethnic groups of differing heights and stature.
    Some medications are calculated using body surface area as opposed to body weight.


    Please fill out required fields.

    Next Steps
    Creator Insights


    Overweight (BMI >25) and obese patients (BMI >30) should be counseled on diet and exercise.


    Body mass index, kg/m2 = weight, kg / (height, m)2

    Body surface area (the Mosteller formula), m2 = [ Height, cm x Weight, kg  / 3600 ]1/2

    Facts & Figures

    BMI, kg/m2 Weight
    <18.5 Underweight
    18.5–24.9 Normal weight
    25.0–29.9 Overweight
    30.0–34.9 Obese

    Class 1
    35.0–39.9 Class 2
    ≥40.0 Class 3

    Adolphe Quetelet

    About the Creator

    The equation was originally created by Adolphe Quetelet, a Belgian, in 1832 as a method to define the standard proportions of the human build. Only in the last half century has the BMI been used as a means to determine body-fat percentage. Ancel Keys, a physiology professor, used Quetelet's equation as part of a 1972 published report on obesity and created the name body mass index or BMI. While widely used in population health studies, the BMI equation has been critiqued for its use in individual diagnoses for determining whether someone is overweight or obese.

    For more on the history of the BMI, check out this article.

    About the Creator
    Adolphe Quetelet