About the Body Surface Area Calculator
This body surface area (BSA) calculator estimates the total surface area of the human body in square metres from height and weight. It reports the Mosteller formula — the most widely used in hospitals — alongside DuBois & DuBois, Haycock, Gehan & George and Boyd, so you can see how closely they agree and pick the one your protocol specifies.
BSA is used to dose chemotherapy and some other drugs, to index cardiac output (cardiac index) and kidney function, and to scale fluid requirements. Nurses, pharmacists, students and patients checking a dosing sheet all use it. For children, Haycock and Mosteller are generally preferred; DuBois is traditional in adults.
Enter metric or imperial measurements. The typical adult BSA is around 1.6–2.0 m². Always follow the formula and rounding rules in your local clinical protocol — this tool is for reference and education.
With the default inputs, the bsa (mosteller) is 1.84 m². Change any value above to recalculate instantly.
How to use the body surface area calculator
- 1Choose metric or imperial units.
- 2Enter height and weight.
- 3Read the Mosteller BSA, or the formula your protocol specifies.
- 4Compare formulas in the chart to see how much they differ for this patient.
Formula and method
Mosteller (1987) simplified earlier work into a square-root formula that is easy to calculate and accurate for adults and children. DuBois & DuBois (1916): 0.007184 × W^0.425 × H^0.725. Haycock (1978): 0.024265 × W^0.5378 × H^0.3964. Gehan & George (1970): 0.0235 × W^0.51456 × H^0.42246. Boyd (1935): 0.0003207 × H^0.3 × (weight in grams)^(0.7285 − 0.0188 × log10 grams).
All take weight W in kilograms and height H in centimetres (except Boyd, which uses grams) and return square metres. For typical adults they agree within a few percent; differences grow at extremes of size, which is why clinical protocols name the formula to use.
- BSA
- Body surface area, m²
- H
- Height in centimetres
- W
- Weight in kilograms
Worked examples
Adult, 175 cm and 70 kg
√(175 × 70 ÷ 3600) = √3.403 = 1.84 m². The other formulas give 1.85 m² (to two decimals), so they agree closely for an average adult.
Imperial: 5 ft 4 in and 130 lb
64 inches is 162.56 cm and 130 lb is 58.97 kg. Mosteller gives √(162.56 × 58.97 ÷ 3600) = 1.63 m², with DuBois almost identical.
Child, 110 cm and 19 kg
For a child, √(110 × 19 ÷ 3600) = 0.76 m². Haycock, validated in infants and children, gives almost the same answer.
Frequently asked questions
What is a normal body surface area?+
Average adult BSA is roughly 1.9 m² for men and 1.6 m² for women. A newborn is about 0.25 m² and a 10-year-old about 1.1 m², depending on size.
Which BSA formula is most accurate?+
No single formula is best for everyone. Mosteller is the most widely used because it is simple and performs well in adults and children; Haycock is often preferred for infants, and DuBois has the longest history in adults.
Why is BSA used for drug dosing?+
Metabolic rate, blood volume and kidney function scale more closely with surface area than with weight, so dosing narrow-therapeutic-index drugs like chemotherapy per m² reduces variation in drug exposure between patients.
How do I calculate BSA by hand?+
Multiply height in centimetres by weight in kilograms, divide by 3,600 and take the square root (Mosteller). For 170 cm and 65 kg: 170 × 65 = 11,050; ÷ 3,600 = 3.07; √3.07 = 1.75 m².
Is BSA capped for chemotherapy?+
Some protocols historically capped BSA at 2.0 m², but current ASCO guidance recommends full weight-based doses for obese adults in most cases. Always follow the regimen protocol and prescriber instructions.
This tool gives general estimates and is not medical advice. Talk to a doctor or qualified professional about your health, diet or training.