Body surface area estimates by formula
Both formulas estimate external body surface area from the same height and weight. Their absolute difference is a comparison, not an error bound or confidence interval. These outputs are not medication doses.
To calculate the different height-and-weight quantity used for adult BMI screening, open the BMI Calculator .
The formula
Height and weight are converted to centimeters and kilograms using exact unit factors before either equation runs. The selected equation supplies the primary result, but both values remain visible. The absolute difference is calculated before display rounding to four decimal places.
Two estimates from the same inputs
At 170 cm and 70 kg, Mosteller gives √(170 × 70 / 3600) = 1.8181 m². Du Bois gives approximately 1.8097 m². Their unrounded absolute difference is approximately 0.0084 m². Selecting Du Bois changes the primary result while retaining both comparisons.
How to use this calculator
- Enter height and body weight in the selected units.
- Choose Mosteller or Du Bois for the primary result.
- Calculate and compare the two estimates and their absolute difference.
Surface area is a different quantity from BMI
Height and weight are shared inputs, but the equations answer different questions. BMI divides mass by squared height; body surface area estimates an area and is expressed in square meters. A BSA value does not provide a body-fat percentage, healthy-weight category, or fitness assessment. It should not be compared with the area of a flat rectangle made from the entered dimensions.
Formula choice can matter in a comparison
Mosteller combines height and weight under a square root. Du Bois applies different exponents to each measurement. Because the models differ, they need not return identical values even from perfectly matching inputs. The calculator prints both values so you can reproduce the selected model when comparing a report. The gap between the estimates does not identify which is closer to a person’s true surface area.
Use the units required by the equations
Both published formulas require centimeters and kilograms in their stated forms. Entering inches into a centimeter field changes the estimate substantially; selecting inches performs the conversion first. The same applies to pounds. The four displayed decimal places make formula comparisons easier, but measurement precision and model error remain separate questions. This tool calculates BSA only: it does not multiply by a medicine dose, cap BSA, adjust for organ function, or interpret a treatment protocol.
Assumptions & limitations
What this calculation assumes
- Uses the uncapped Mosteller and Du Bois equations with the same entered measurements.
What to keep in mind
- Height and weight are bounded inputs; no assessment of model suitability for an individual is performed.
- Does not calculate medication doses or apply pediatric, clinical, or protocol-specific corrections.
- The difference between formulas is not a measurement-error estimate.
Common questions
Which formula supplies the main result?
The formula selected in the form. Both formula outputs stay visible for comparison.
Does BSA use kilograms or pounds?
The equations use kilograms internally. If you choose pounds, the calculator converts your weight before evaluating them.
Can I use the result to calculate a medicine dose?
This page provides an area estimate only. It does not implement dosing instructions, clinical eligibility checks, or treatment-specific adjustments.