What body surface area is used for
Body surface area (BSA) estimates the total area of your skin in square metres, worked out from height and weight. A typical adult lands somewhere around 1.6 to 2.0 m² — far more than intuition suggests, because skin folds over a three-dimensional body. Clinicians use BSA because many things scale with surface area better than with weight alone: metabolic rate, cardiac output, kidney function, burn severity (which is assessed as a percentage of BSA burned), and the dosing of certain medicines, most famously chemotherapy agents, which are often prescribed in milligrams per square metre. If a clinic letter or a dosing chart quotes your BSA, this page shows exactly which arithmetic produced it.
The Mosteller and DuBois formulas
The DuBois formula (1916) is the original, fitted a century ago from a small group of subjects measured by covering them in moulds — heroic, but a tiny sample. The Mosteller formula (1987) replaced it in most modern practice not because it is dramatically more accurate, but because it is a single square root that a busy clinician can compute and check without fractional exponents, and validation studies found it performs about as well. For typical adult builds the two agree within a percent or two, as the defaults here show: Mosteller gives exactly 2.00 m² for 180 cm and 80 kg, and DuBois about 1.996 m².
Where the formulas bend
Both equations were fitted on limited populations, and both are estimates of a quantity nobody measures directly in routine care. They drift apart at the extremes — very tall, very short, very heavy or very light bodies, and children — sometimes by several percent. Pediatric practice often prefers formulas fitted on children, and burn or oncology units follow their own institutional standard, which is the right approach: in real dosing, consistency with the protocol matters more than which respectable formula generated the number. Also note that BSA responds to both inputs but not equally: because height and weight enter Mosteller symmetrically under a square root, a 10 percent rise in either one lifts BSA by about 5 percent.
Reading your result in context
For a healthy adult, BSA by itself is neither good nor bad — it is a size descriptor, like height, not a health score. It earns its keep when something else is expressed relative to it: a cardiac index (cardiac output divided by BSA), a kidney function estimate normalised to a standard 1.73 m², or a drug dose per square metre. If you are here because a medication or a trial protocol quotes BSA, bring this figure to your care team rather than adjusting anything yourself: this calculator gives general information only and is not medical advice, and dosing decisions belong to the professionals who know the full picture.
Worked example
A person 180 cm tall weighing 80 kg. Mosteller: √(180 × 80 ÷ 3,600) = √(14,400 ÷ 3,600) = √4 = 2.00 m² exactly. DuBois: 0.007184 × 1800.725 × 800.425 ≈ 1.996 m² — the century-old formula and the modern shortcut agree to within a fifth of one percent here.
How to use this calculator
- Enter your weight in kilograms.
- Enter your height in centimetres.
- Read the Mosteller body surface area in the headline panel.
- Compare the DuBois result in the breakdown — a close match is expected for typical adult builds.
- If a clinician or protocol gave you a BSA-based figure, check which formula they used before comparing numbers.
A short history of measuring skin
The DuBois formula's origin is one of the odder stories in measurement science: in 1916, Delafield DuBois and Eugene DuBois estimated surface area by making paper moulds of a handful of subjects' bodies, flattening them and measuring the pieces. That nine-subject foundation, refinements and all, served medicine for most of a century — a reminder that a formula's longevity reflects usefulness and convenience as much as precision. Later formulas, including Mosteller's simplification and several fitted on larger, more diverse samples, all land close together for average adults because the underlying geometry is forgiving: surface area scales predictably with size.
Practically, the lesson is to relax about small differences. If two respectable formulas give you 1.99 and 2.00 m², nothing of consequence hangs on the gap. Where BSA feeds a real clinical calculation, the treating team will use their standard formula and their standard rounding — your job is simply to recognise the number when you meet it, which you now can.
Important note
For information only — not medical advice. This calculator uses standard published formulas to estimate values for general education and planning. It does not diagnose, treat, or replace the advice of a doctor or other qualified health professional. If you have a health concern, are pregnant, or are making decisions about treatment, medication, or a major diet or exercise change, please talk to a healthcare professional first.