Body Surface Area Calculator (BSA)
Body surface area (BSA) calculator for Singapore — enter height and weight to get BSA from the Mosteller, Du Bois and Haycock formulas, used in chemotherapy dosing, paediatric drug calculation and cardiac index. Educational reference; runs in your browser.
Body Surface Area Calculator (BSA)
Enter height and weight — the calculator returns body surface area in m² from three published formulas. The Mosteller result is shown as the headline.
Please tick the acknowledgement above before calculating.
- Curriculum
- English (Singapore) — Singapore Examinations and Assessment Board (SEAB)
- Built against
- Singapore clinical practice — chemotherapy (mg/m²) and paediatric dosing
- Unit system
- SI primary; US/imperial readout below
- First published
- 27 May 2026
- Last updated
- 13 Sep 2026
View authoritative scientific sources
- Mosteller RD. Simplified calculation of body-surface area. N Engl J Med 1987;317(17):1098
- Du Bois D, Du Bois EF. A formula to estimate the approximate surface area if height and weight be known. Arch Intern Med 1916;17:863-871
- Haycock GB, Schwartz GJ, Wisotsky DH. Geometric method for measuring body surface area. J Pediatr 1978;93(1):62-66
- Verbraecken J, Van de Heyning P, De Backer W, Van Gaal L. Body surface area in normal-weight, overweight, and obese adults. A comparison study. Metabolism 2006;55(4):515-524
⚠️ Educational use only — see full disclaimer
EDUCATIONAL USE DISCLAIMER
This calculator is provided for educational and reference purposes only. It is not a substitute for instruction from a qualified teacher, your prescribed textbook, or your school's official curriculum materials.
When preparing for examinations, always cross-check our calculations and notation against your current syllabus and your teacher's guidance. Syllabus conventions and accepted notation vary between curricula and may change between examination years.
If you believe any calculation, notation, or curriculum reference in this tool is inaccurate, please let us know via the feedback button. We review feedback promptly and update tools when verified corrections are needed.
RECATOOLS accepts no liability for academic, examination, professional, or research outcomes arising from use of this tool.
How to Use the BSA Calculator
Enter height and weight
Type the patient’s height and weight, choosing cm or inches and kg or pounds. The calculator converts internally to centimetres and kilograms.
Acknowledge, then read the BSA
Tick the acknowledgement box before calculating — results stay hidden until you confirm this is not a diagnosis. The headline then shows the Mosteller BSA in m², the formula most used clinically in Singapore for chemotherapy dosing, with Du Bois and Haycock alongside.
Pick the right formula
Mosteller is the everyday default; Du Bois is the classic reference; Haycock is validated for paediatric patients. Use whichever your protocol specifies.
Check against your protocol
The Tool Information block lists the source formulas. This is an educational reference, not a substitute for your hospital’s dosing protocol or a pharmacist’s check.
Body Surface Area in Clinical Dosing
Body Surface Area (Mosteller)
Example: A patient is 170 cm tall and weighs 70 kg. Find the body surface area using the Mosteller formula.
Using BSA = √(height × weight / 3600):
BSA = √(170 × 70 / 3600) = √3.306 ≈ 1.82 m²
Body surface area (BSA) is the total external area of the body, expressed in square metres. It is preferred over body weight alone for scaling many drug doses — especially cytotoxic chemotherapy, where doses are written in mg/m² — because BSA tracks metabolic rate, cardiac output and renal function more closely than weight does. A typical adult BSA is around 1.7 m², which is why 1.73 m² is the standard reference value used when indexing kidney function (eGFR) and cardiac index. Because BSA cannot be measured directly in routine practice, it is estimated from height and weight using validated formulas.
This calculator gives three of the most widely used estimates side by side. The Mosteller formula, BSA = √(height × weight / 3600), is the simplest and the one most clinicians reach for; it is shown as the headline result. The Du Bois formula from 1916 is the historical reference still cited in many texts, and the Haycock formula is validated down to small infants, making it the usual choice in paediatrics. The three usually agree to within a few percent for average adults but can diverge at the extremes of body size, which is why your local protocol specifies which formula to use. All calculation happens in your browser, so no patient data is uploaded and the tool works offline once loaded.
Chemotherapy is dosed in mg/m², not mg/kg — which is why an accurate body surface area matters so much in oncology.
Body surface area tracks metabolism better than weight does
BSA is the body’s total external area in m².
Mosteller: BSA = √(height × weight / 3600).
A typical adult BSA is about 1.7 m².
Chemotherapy doses are written in mg/m².
eGFR is indexed to 1.73 m².
Du Bois dates from 1916.
Haycock (1978) is validated for infants.
BSA tracks metabolic rate better than weight.
Cardiac index = cardiac output ÷ BSA.
This tool runs in your browser — no patient data is uploaded.
Frequently Asked Questions
- Body surface area (BSA) is the total external area of a person’s body, expressed in square metres. It is widely used in medicine to scale drug doses and to index physiological measurements such as cardiac output and kidney function, because it correlates better with metabolic processes than body weight alone.
- The Mosteller formula is the everyday clinical default and is shown as the headline here. Du Bois is the classic 1916 reference still quoted in many textbooks, and Haycock is validated for paediatric patients, including small infants. For average adults all three agree closely; at the extremes of body size they diverge, so follow whichever your hospital protocol specifies.
- Mosteller’s 1987 formula is BSA = √(height in cm × weight in kg / 3600). Its appeal is that it can be done on a simple calculator and is accurate enough for routine dosing. For a 170 cm, 70 kg adult it gives about 1.82 m².
- Cytotoxic drugs have a narrow therapeutic window, and BSA tracks the parameters that govern drug handling — metabolic rate, blood volume and organ function — more closely than weight. Writing doses in mg/m² gives a more consistent exposure across patients of different sizes, which is why oncology protocols are built around BSA.
- A typical adult has a BSA of roughly 1.6–2.0 m², with about 1.7 m² often quoted as average. The value 1.73 m² is the conventional reference used when indexing estimated glomerular filtration rate (eGFR) and cardiac index, so results are comparable between people of different sizes.
- Yes. Choose pounds or kilograms for weight and inches or centimetres for height — the calculator converts to kilograms and centimetres before applying each formula, so you get the same BSA regardless of which units you enter.
- These formulas estimate BSA from height and weight; they are not direct measurements. For average-sized adults they are accurate to within a few percent of each other. Accuracy falls at the extremes of body habitus, in oedema, and in very small children, which is why protocols often specify a particular formula and sometimes cap the dose.
- No. It is an educational and reference aid for checking a calculation. Actual prescribing and dose verification must follow your institution’s protocol and be checked by a qualified clinician or pharmacist. Nothing here constitutes medical advice.
- No. Every calculation runs entirely in your browser; the height and weight you enter are never uploaded. The tool works offline once the page has loaded.
- Each was fitted to a different sample. Du Bois and Du Bois (1916) measured nine people; Haycock and colleagues (1978) fitted 81 subjects from infants to adults; Mosteller (1987) simplified an earlier formula so it could be worked on a pocket calculator. They agree within a few percent for average adults, and comparison studies in overweight and obese adults (Verbraecken et al., Metabolism 2006) show the gap widening at higher body weights — which is why a dosing protocol names the formula it wants.
Method & sources
How it computes
Body surface area (m²) from height (cm) and weight (kg) by three published formulas, Mosteller as the headline: Mosteller BSA = √(H × W ÷ 3600); Du Bois BSA = 0.007184 × W^0.425 × H^0.725; Haycock BSA = 0.024265 × W^0.5378 × H^0.3964. Inputs in inches or pounds are converted first (1 in = 2.54 cm; 1 lb = 0.45359237 kg).
What this tool implements
- Mosteller RD (1987): BSA = √(height cm × weight kg / 3600) — headline result.
- Du Bois D, Du Bois EF (1916): BSA = 0.007184 × W^0.425 × H^0.725.
- Haycock GB, Schwartz GJ, Wisotsky DH (1978): BSA = 0.024265 × W^0.5378 × H^0.3964, validated from infants to adults.
- Educational reference only; results gated behind a medical acknowledgement and shown with a physician CTA; 1.73 m² quoted as the eGFR/cardiac-index reference surface.
Sources
- Mosteller RD. Simplified calculation of body-surface area. N Engl J Med 1987;317(17):1098. PMID 3657876. doi:10.1056/NEJM198710223171717
- Du Bois D, Du Bois EF. A formula to estimate the approximate surface area if height and weight be known. Arch Intern Med 1916;17:863-871.
- Haycock GB, Schwartz GJ, Wisotsky DH. Geometric method for measuring body surface area: a height-weight formula validated in infants, children, and adults. J Pediatr 1978;93(1):62-66.
- Verbraecken J, Van de Heyning P, De Backer W, Van Gaal L. Body surface area in normal-weight, overweight, and obese adults. A comparison study. Metabolism 2006;55(4):515-524. PMID 16546483.
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