Body Surface Area (BSA) Calculator
Calculate body surface area in m² from your height and weight, using both the Mosteller and Du Bois formulas. BSA is used to dose many medications (including chemotherapy) and to index physiological measurements. Enter height and weight in metric or imperial units.
The BSA formulas
Mosteller: BSA (m²) = √(height[cm] × weight[kg] ÷ 3600). Du Bois: BSA = 0.007184 × height[cm]0.725 × weight[kg]0.425. Sources: Mosteller RD, N Engl J Med 1987; Du Bois D & Du Bois EF, Arch Intern Med 1916.
Frequently asked questions
How is body surface area calculated?
The Mosteller formula is BSA (m²) = √(height in cm × weight in kg ÷ 3600). The Du Bois formula is BSA = 0.007184 × height(cm)⁰·⁷²⁵ × weight(kg)⁰·⁴²⁵. For a 170 cm, 70 kg adult both give about 1.81–1.82 m². The Mosteller formula is simplest and the most widely used.
What is an average body surface area?
Average adult BSA is often quoted as about 1.7 m² — roughly 1.9 m² for men and 1.6 m² for women. Many physiological measurements, such as cardiac index and eGFR, are indexed to a reference BSA of 1.73 m². The real spread is much wider than that single average suggests: by the Mosteller formula a 3.5 kg, 50 cm newborn comes out at about 0.22 m², while a 190 cm, 110 kg adult comes out at about 2.41 m². That is why anything indexed to 1.73 m² drifts furthest at the extremes of body size.
Which formula should I use — Mosteller or Du Bois?
Both Mosteller and Du Bois are accepted. Mosteller is the easiest to compute and is common for chemotherapy dosing; Du Bois (from 1916) is the classic reference. They usually agree to within a few percent. This calculator shows both so you can compare.
Why is BSA used to dose drugs?
BSA correlates better than body weight alone with metabolic rate, blood volume and renal function, so it is used to individualise doses of drugs with a narrow safety margin — chemotherapy above all. Dosing decisions always belong with the prescribing clinician. In practice the dose is written in mg per m² and multiplied by the patient’s BSA, so a 1.8 m² adult prescribed 100 mg/m² receives 180 mg. Some protocols cap or adjust the BSA used for dosing at the extremes of body size, where the relationship between surface area and drug handling weakens.
Does this work in feet, inches and pounds?
Imperial units are supported directly by this BSA calculator’s unit toggle. Switch it to Imperial to enter height in inches and weight in pounds; the calculator converts to centimetres and kilograms internally (× 2.54 and × 0.45359237) before applying the formulas. Feet must be turned into inches first — 5 ft 7 in is 67 inches. Both formulas are defined in centimetres and kilograms, so metric and imperial entry give the same BSA for the same body.
This is a reference tool, not a diagnosis or medical advice. Results depend on the laboratory, assay and clinical context, and reference intervals vary between labs and by age and sex — always read your result against the range printed on your own report and discuss it with a qualified healthcare professional.
More medical calculators
eGFRCreatinine ClearanceCorrected CalciumAnion GapA1C to eAGHOMA-IRQUICKIGMICholesterol RatioMean Arterial PressureQTcWaist-to-Hip RatioWaist-to-Height RatioLean Body MassPack-YearVO₂ MaxMELD ScoreFramingham RiskASCVD RiskCHA₂DS₂-VAScHAS-BLEDWells DVTWells PEMELD 3.0PREVENT RiskCHA₂DS₂-VAGeneva ScorePERC RuleChild-PughCURB-65Glasgow Coma (GCS)FIB-4 IndexCorrected SodiumSerum OsmolalityAPRIFatty Liver IndexNAFLD Fibrosis ScoreCentor ScoreFeNaqSOFALVH (ECG)ESR (VSH)Thymol TurbidityMaddrey's DFA-a GradientNEWS2ANCWinters' FormulaShock IndexAlvarado ScoreReticulocyte IndexFree Water DeficitPadua ScoreGlasgow-BlatchfordCIWA-ArMMEMaintenance FluidsBishop ScoreVancomycinSteroid ConversionHEART ScorePediatric DoseSOFA ScoreTransferrin SaturationSF Syncope RuleParkland FormulaInsulin CorrectionCaprini ScoreNIHSSPSI / PORT Lab unit converters →