Body Surface Area Calculator.

How the Body Surface Area Calculator works.

Equation, units, and population

BSA (m²) = √((height cm × weight kg) ÷ 3600). Height is entered in centimetres and weight in kilograms. The output is square metres. This page names the equation rather than presenting an unexplained score. Check that every value uses the displayed unit and that you belong to the population for which the method is described. The calculation retains full precision internally and rounds only the visible result. A reproducible estimate should let another reader use the same inputs and reach the same arithmetic answer, while still recognizing that mathematical reproducibility does not prove medical suitability.

Worked example

At 175 cm and 70 kg, the Mosteller calculation is √((175 × 70) ÷ 3600), which is approximately 1.84 m². Work through the example by writing the equation, substituting each labeled input, and preserving units at every step. The example demonstrates arithmetic only; it is not a recommended body measurement, intake, exercise level, laboratory value, or date. Replace every example input with the values from the situation being considered, and retain those inputs with any result you copy. Small differences can arise from rounding, equation versions, atomic-weight conventions, or date boundaries.

What the result means

BSA is a size-normalization estimate used in some clinical and physiological contexts. A larger or smaller value is not itself a health rating. Use the result only for the purpose named on this page and keep the equation, population, and measurement conditions consistent when comparing values over time. If it conflicts with symptoms, a laboratory report, a clinician’s instructions, or a validated measurement, use the appropriate professional evidence rather than this calculator.

Validation and edge cases

The calculator accepts weight from 1–300 kg and height from 30–250 cm, rejects blanks and nonfinite values, and reports the result to two decimal places. Blank, malformed, nonfinite, and out-of-domain inputs fail explicitly without producing NaN or infinity. The bounds prevent obviously implausible values from being mistaken for meaningful answers, but passing a range check does not make an input medically correct. Recheck dates, decimal separators, unit conversions, coefficient choices, and whether a laboratory value uses the expected assay and unit. Contact a qualified professional when a result could affect treatment, medication, pregnancy care, nutrition therapy, or exercise safety.

Limitations and responsible use

Body surface area formulas approximate body size and can differ at extremes of age, body composition, or size. Clinical protocols may specify another equation or a measured value. This is an educational estimate. Do not calculate medication doses or treatment decisions without a clinician or pharmacist. FigureNest processes these inputs locally in the browser and does not send them to a calculation service. The page does not create a medical record, assess symptoms, or know personal history. Avoid using estimates to shame a body, pursue unsafe restriction, delay care, determine legal fitness, or replace contraception. Authoritative source links are provided so readers can check the equation version and current guidance before making a consequential decision.

What this tool does not include.

Body surface area formulas approximate body size and can differ at extremes of age, body composition, or size. Clinical protocols may specify another equation or a measured value.

Reference guidance and methodology.

• PubMed — Simplified Body-Surface Area Calculation (opens in a new tab)