Body Surface Area (BSA) Calculator
What is my body surface area?
Result
How it is calculated
Body surface area (BSA) estimates the skin area of the body in square metres. The tool shows two classic formulas side by side. Mosteller: BSA = √(height × weight / 3600), with height in centimetres and weight in kilograms. Du Bois: BSA = 0.007184 × height0.725 × weight0.425, with the same units. Both results are rounded to two decimals and shown in m². Height and weight must be above zero. The two formulas usually agree within a few hundredths of a square metre for adults of average build; they can drift apart for very small or very large bodies. BSA is a population estimate, not a measurement of one person.
Worked example
Take a height of 175 cm and a weight of 70 kg. Mosteller: 175 × 70 = 12,250; divided by 3,600 this is 3.4028, and its square root is 1.84 m². Du Bois: 1750.725 ≈ 42.2 and 700.425 ≈ 6.08; multiplied by 0.007184 this gives 1.85 m². The two methods differ by only about 0.01 m² for this body size.
Common mistakes
- Entering height in metres (1.75) or feet and inches; both formulas expect centimetres.
- Entering weight in pounds instead of kilograms, which inflates the area by more than 2 times.
- Swapping the two fields, which changes the Du Bois result because the exponents differ for height and weight.
- Mixing the two formulas: a dose or reference range quoted for one formula should be compared with that formula's value.
- Using the figure as a clinical dose on its own; it is only an estimate and any medical dosing must follow the prescriber's instructions.
About this calculator
This calculator estimates body surface area (BSA) — the total external area of the human body, expressed in square meters — from height and weight, using the Mosteller and Du Bois formulas, two widely validated methods that give closely matching results for most adults.
BSA matters most in clinical medicine: it is the standard way doctors and pharmacists scale chemotherapy drug dosing and certain other medications, since dosing by body weight alone can be less accurate for drugs that act on tissue surface. It is also used in burn-injury assessment and some physiological and cardiac index calculations.
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