Build live 2026 estimates with USA, UK, metric, and imperial options for body surface area calculator.
Body Surface Area (BSA) is the measured or calculated surface area of a person's body, expressed in square metres (m²). Because it correlates with metabolic mass better than weight alone, it is used in drug dosing (especially chemotherapy), cardiac index calculations, burn assessment, and fluid resuscitation — in both US and UK clinical practice.
This calculator supports the three most widely used equations. Each was derived from different populations and can give slightly different results, so your clinician will specify which formula to use.
BSA = √((Height cm × Weight kg) ÷ 3600). Simple, fast, and the most common default in modern oncology. Works well across adults.BSA = 0.007184 × Height^0.725 × Weight^0.425. The historical standard; still referenced in many UK and US drug monographs.BSA = 0.024265 × Height^0.3964 × Weight^0.5378. Preferred for infants and children because it was derived using paediatric subjects.In the United States, chemotherapy and many targeted therapy doses are prescribed as mg/m². The Mosteller formula is used by most US cancer centres because of its simplicity. FDA drug labels routinely specify dosing per BSA — for example, paclitaxel 175 mg/m² or doxorubicin 60 mg/m². For patients with BMI > 35, some protocols cap BSA at 2.0 m² to avoid overdosing; always follow the prescribing guideline.
The NHS and UK hospital formularies also dose chemotherapy, biologic agents, and paediatric medicines per m². The British National Formulary (BNF) and BNFc give worked examples using either Mosteller or Du Bois. For children, the Haycock equation is commonly preferred. UK cardiac imaging reports (echo and MRI) routinely index stroke volume and cardiac output to BSA to give cardiac index (L/min/m²).
Average adult BSA is around 1.6–2.0 m². A 70 kg, 170 cm adult has a Mosteller BSA of about 1.81 m². Children are much smaller — a 20 kg, 110 cm child has a BSA of about 0.78 m² (Haycock).
For routine adult dosing, the Mosteller and Du Bois formulas agree within about 1–3%. Mosteller is preferred because it's easy to calculate by hand. For children, Haycock is slightly more accurate because its reference population included infants.
For adult men, typical BSA is 1.9–2.0 m². For adult women, it's 1.6–1.7 m². Values above 2.4 m² or below 1.3 m² in an adult should prompt a review of how the body dimensions were measured.
Multiply your BSA (m²) by the drug's mg/m² dose. Example: BSA of 1.85 m² × 175 mg/m² paclitaxel = 324 mg total dose. Always cross-check against the protocol — some drugs have dose caps, rounding rules, or require dose reduction for organ function.
No. BMI is weight (kg) ÷ height (m)² — a ratio used to classify underweight/overweight. BSA is an estimated surface area in m² used for dosing and physiologic indexing. They are different measures and cannot substitute for each other.
This tool expects centimetres and kilograms. Convert first: height in cm = feet × 30.48 + inches × 2.54; weight in kg = pounds × 0.4536. A future update will add inline unit switching.
This body surface area tool provides estimates for informational purposes only and is not a substitute for professional dosing, prescribing, or medical judgment. Height, weight, formula selection, and treatment context all affect how BSA is used clinically.
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