Body Surface Area Calculator - Mosteller, Du Bois, Haycock

A body surface area calculator estimates how many square metres of skin-like surface empirical formulas assign to a given standing height and body weight. The three equations on this page are Mosteller, Du Bois, and Haycock. They are physiology and teaching tools. They are not a drug-dose calculator. Chemotherapy, targeted therapy, and many other medicines that historically used mg/m² belong with a licensed oncology or clinical team, a verified height and weight, and the protocol in force - not with a public website.

The default inputs are 180 cm and 80 kg. Mosteller is √((Hcm × Wkg) / 3600) = √((180 × 80) / 3600) = √(14400 / 3600) = √4 = 2.00 m² exactly. That identity is why those defaults exist: you can audit the square root without a spreadsheet. Du Bois and Haycock sit near 2.00 m² on the same person but are not identical; both are printed so the spread is visible.

Do not confuse BSA (m²) with BMI (kg/m²). BMI on the BMI calculator is a Quetelet screening index. BSA is an estimated area. Lean mass in kilograms is a third quantity on the lean body mass calculator. Mixing the three in one sentence is how dosing errors start in amateur spreadsheets.

This is not medical advice and not a burn-chart substitute. Lund–Browder and Wallace “rule of nines” estimate fraction of body surface burned; they do not replace Mosteller for total m², and this page does not implement burn assessment.

1. Choose metric (cm, kg) or imperial (feet, leftover inches, pounds). Formulas always run in centimetres and kilograms.
2. Enter current standing height and a recent weight. Morning weight is more repeatable; edema and casts distort BSA the same way they distort weight.
3. Read Mosteller, Du Bois, and Haycock in m². Copy if you need a study note. Do not convert those square metres into milligrams.
4. Inputs stay in this browser for up to 30 days and are never uploaded.

Mosteller (1987) is a simplification that became popular because it is hard to mis-type and because 180 cm / 80 kg lands on a round 2.00 m². Du Bois and Du Bois (1916) used a power product fitted on a small early-20th-century sample; it remains cited in textbooks. Haycock et al. (1978) fitted a form that behaves more kindly across a wider pediatric-to-adult range in their data. On 80 kg and 180 cm, Du Bois is about 2.00 m² (≈ 1.996) and Haycock about 2.01 m² (≈ 2.007). The second decimal is not a laboratory grade.

Imperial path: convert inches × 2.54 to cm and pounds / 2.2046226218 to kg, then apply the same three formulas. Putting 70 inches into the centimetre slot of Mosteller would compute √((70 × 80) / 3600) ≈ 1.25 m², which is the BSA of a much smaller body - a unit disaster, not a “US formula.”

Other named BSA equations exist (Boyd, Gehan and George, Fujimoto, Schlich). They are not implemented here. If a protocol names Du Bois, do not silently switch to Mosteller because the website default is prettier.

Many cytotoxic regimens were historically ordered as milligrams per square metre of BSA. That convention is under debate: flat dosing, AUC targets, renal adjustment, and toxicity-guided dosing compete with BSA in modern practice. None of that debate is resolved by printing 2.00 m² on a hobby calculator. If you are a patient, the dose you receive is the dose your team calculated in their system, not a number from DevOkk.

Physiology uses BSA as a normalizer: cardiac index is cardiac output divided by BSA; some GFR normalizations use 1.73 m² as a standard adult area. Those are definitions in a report, not buttons on this form. We will not output “your cardiac index” or “your GFR.”

Extreme obesity, amputation, anasarca, pregnancy, and intensive-care fluid loads make height–weight BSA a poor proxy for actual skin or for volume of distribution. Adjusted body weight and other clinical fudge factors are not encoded here on purpose.

Related educational tools: healthy weight, ideal weight, BMR, calories. Tape adiposity is on the body fat calculator and the Army body fat calculator.

More Mosteller checks: 170 cm / 70 kg → √((170×70)/3600) = √3.3056 ≈ 1.82 m². 160 cm / 55 kg → √(2.444) ≈ 1.56 m². 190 cm / 90 kg → √(4.750) ≈ 2.18 m². 150 cm / 45 kg → √(1.875) ≈ 1.37 m². 175 cm / 70 kg → √(3.403) ≈ 1.84 m² (the BMI-page example). Du Bois and Haycock will drift by a few hundredths on each of those.

Search traffic asks “Mosteller formula,” “BSA calculator mg m2,” and “average body surface area.” Average adult BSA is often cited near 1.7–1.9 m² in older European samples and near 2.0 m² in heavier contemporary cohorts - a statistic, not a target. “BSA calculator mg m2” is the query this page exists to disappoint: we calculate m² and stop.

A larger BSA is not “unhealthier.” Taller people have more estimated area at the same BMI. Shame is not a feature. If medications, cancer treatment, or body size are causing distress, that conversation is clinical. This form will not dose, diagnose, or rank you.

Privacy: JavaScript only, unique localStorage key for this slug, 30-day expiry, no upload. After the page loads, the three formulas still run if the network drops. There is no eval and no server-side height/weight log.

Laboratory reports often “index” kidney function to 1.73 m², a conventional standard adult surface from mid-20th-century reference populations. That number is not Mosteller on 180/80 (which is 2.00). It is not a goal BSA. If a lab already printed eGFR in mL/min/1.73 m², this calculator will not back-solve your unindexed GFR. Do not multiply or divide clinical lab values using a web Mosteller unless a clinician told you exactly which algebra to use.

Haycock was motivated in part by pediatric and mixed-age samples. This page still presents it as an educational adult companion to Mosteller and Du Bois, not as a validated pediatric growth tool. Neonates and children have different geometry; Boyd and other pediatric BSA formulas exist in the literature and are not implemented here. Typing a 90 cm / 12 kg child into Mosteller will produce a small m²; that does not make this a pediatric dosing page. We refuse the dosing job for every age.

Imperial traps: 5 ft 11 in is 71 inches = 180.34 cm, not 180. 176 lb is about 79.83 kg, not 80. Mosteller on those imperial defaults will be very close to 2.00 but not the exact √4 identity. If a homework problem says 180 cm and 80 kg, use metric. If a US chart lists inches and pounds, convert once, then apply the named formula. Mixing 70 inches with 80 kg inside √((H×W)/3600) without converting H is the classic error.

Cardiac output divided by BSA is cardiac index. Stroke volume index is similar. Those definitions assume a BSA your lab or catheter software already computed, often Du Bois in older machines and Mosteller in newer ones. A 0.02 m² disagreement between formulas is a few percent on a 2.00 m² adult - enough to bother a metrologist, not enough for this page to pick a winner. We show all three so you see the spread instead of worshipping one default.

Burn care uses percent of BSA burned, not total m² from Mosteller, as the first-line field number. Rule of nines and palmar methods estimate the fraction. Fluid formulas (Parkland and successors) then use weight and percent burned. This calculator does not implement those pathways and must not be used to invent a fluid rate. Emergency care is not a JavaScript form.

Obesity and BSA: as weight rises at fixed height, Mosteller grows with the square root of weight, Du Bois with weight^0.425, Haycock with weight^0.5378. They fan out. Some clinicians prefer adjusted body weight for certain drugs instead of BSA; that is a protocol choice this page will not encode. Extreme BMI is a reason to distrust a height–weight surface as a proxy for metabolic size, not a reason to hunt for a fourth equation on a random website.

Relationship to other tools: estimated skin area is not fat percentage (body fat), not Army tape (Army body fat), not Boer kilograms (lean body mass), and not a healthy-weight band (healthy weight). Keep the question and the unit in the same sentence: m² here, kg there, kg/m² on BMI, percent on tape.

Extra Du Bois / Haycock on the default: 0.007184 × 80^0.425 × 180^0.725 ≈ 1.996 m²; 0.024265 × 80^0.5378 × 180^0.3964 ≈ 2.007 m². Mosteller is exactly 2. Display rounding to two decimals may print 2.00 for all three on some locales; the underlying values still differ. Copy text includes two-decimal m² plus the clinical refusal sentence so a pasted result cannot be mistaken for an order.

Temperature, humidity, and clothing do not enter Mosteller. Only height and weight do. A winter coat on the scale is a weight error, not a climate correction. Measure as you would for a clinic visit: light clothing or gown, shoes off, stadiometer if you have one. Home tape-height is noisier than a wall-mounted rod; BSA will inherit that noise through H^0.725 on Du Bois.

Sex is not an input on this BSA page. Mosteller, Du Bois, and Haycock as implemented here are height–weight formulas without a sex coefficient. Some later BSA fits add sex; they are not on this form. Do not “adjust” 2.00 m² up or down because of a stereotype about male or female area. If a paper you are reading uses a sexed BSA, use that paper’s equation, not a mental fudge on Mosteller.

Amputation and wheelchairs: standing height may be unavailable or misleading. Demispan, knee height, and other proxies exist in anthropometry; this tool does not convert them. Do not invent a height to force a BSA for a dosing conversation - that conversation should already have left the browser.

Storage key body-surface-area-calculator-data is unique. The split class body-surface-area-split-track is unique. Fullscreen shows the three m² values without the article. After load, the page still computes if the network drops. That offline property is for homework, not for a clinic that has lost connectivity during a real infusion.

If a homework set asks only for Mosteller, still glance at Du Bois and Haycock so you remember they exist. If a protocol names one formula, use that name in your write-up. The 2.00 m² default is a square-root identity, not an average human, not a dosing constant, and not permission to compute milligrams on a public site.

Confirm the identity after reload: 180 cm and 80 kg must still show Mosteller 2.00 m². Du Bois should sit near 1.996 m² and Haycock near 2.007 m² before two-decimal rounding. If all three print identical values to many decimals, the implementation collapsed formulas and should not be trusted for study notes either.