Body measurements
BSA calculator: body surface area from height and weight
Enter height and weight to get body surface area (BSA) in square metres by the Mosteller formula, with the Du Bois and Haycock results beside it. The page also shows each formula, a worked example and a table comparing the three, so you can check a number by hand.
Enter your values above to see your result and what it means.
BSA formula: Mosteller, Du Bois and Haycock
The Mosteller formula, published as a letter in the New England Journal of Medicine in 1987, is the simplest: BSA (m²) = √(height in cm × weight in kg / 3600). The Du Bois formula (1916) is BSA = 0.007184 × weight^0.425 × height^0.725. The Haycock formula (1978), checked against measurements in 81 people from premature babies to adults, is BSA = 0.024265 × weight^0.5378 × height^0.3964. Worked example with Mosteller: at 180 cm and 80 kg, 180 × 80 = 14,400; divided by 3600 that is 4; the square root of 4 is 2.00 m².
| Height and weight | Mosteller | Du Bois | Haycock |
|---|---|---|---|
| 50 cm, 3.5 kg (newborn) | 0.22 | 0.21 | 0.22 |
| 110 cm, 18 kg (young child) | 0.74 | 0.74 | 0.74 |
| 160 cm, 55 kg | 1.56 | 1.56 | 1.57 |
| 170 cm, 70 kg | 1.82 | 1.81 | 1.83 |
| 180 cm, 80 kg | 2.00 | 2.00 | 2.01 |
| 190 cm, 100 kg | 2.30 | 2.28 | 2.31 |
How to calculate BSA in pounds and inches
Convert first: inches × 2.54 gives centimetres and pounds × 0.4536 gives kilograms. For someone 5 ft 10 in (70 in, 177.8 cm) and 180 lb (81.6 kg), Mosteller gives √(177.8 × 81.6 / 3600) = 2.01 m². The calculator does the conversion for you when you switch to imperial units.
What is an average body surface area?
There is no normal range for BSA, because it simply reflects size. For context, a study of 3,613 adults receiving chemotherapy at three UK cancer centres in 2005 found an average BSA of 1.79 m²: 1.91 m² in men and 1.71 m² in women. Those are averages from one group of patients, and many healthy people sit well above or below them.
| Group | Mean BSA |
|---|---|
| All adults (n = 3,613) | 1.79 m² |
| Men | 1.91 m² |
| Women | 1.71 m² |
Where body surface area is used
The majority of chemotherapy drugs are dosed according to BSA, which is why oncology teams measure height and weight before treatment. BSA is also used to index cardiac output: the cardiac index is cardiac output divided by BSA, in litres per minute per square metre, so that heart function can be compared between people of different sizes. Doses and indexed values are worked out by the clinical team; this page explains the measurement only.
Frequently asked questions
What is the formula for body surface area?
The simplest is the Mosteller formula: BSA (m²) = √(height in cm × weight in kg / 3600). At 170 cm and 70 kg it gives 1.82 m². It agrees with the older Du Bois formula to within 0.02 m² in the adult examples above, and this calculator shows both, plus Haycock.
What is a normal body surface area?
BSA has no normal or abnormal range; it describes body size. As a point of reference, adults treated with chemotherapy in three UK centres averaged 1.79 m² (1.91 m² for men, 1.71 m² for women).
Which is more accurate, Mosteller or Du Bois?
For adults of average build the two usually differ by about 0.01 to 0.02 m². In small children and babies, Haycock and colleagues found that Du Bois increasingly underestimates surface area below about 0.7 m², by nearly 8% in newborns, while their own formula fitted measured values from under 0.2 m² to over 2.0 m².
Why is BSA used for chemotherapy?
Most chemotherapy drugs are dosed per square metre of body surface area, so the treating team calculates BSA from measured height and weight before treatment. The dose itself is set by the oncology team; a calculator like this one should never be used to work it out.
What is the cardiac index?
The cardiac index is cardiac output divided by body surface area, expressed in litres per minute per square metre. Dividing by BSA lets clinicians compare heart output between people of different sizes.
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. 1916. Reprinted in Nutrition. 1989;5(5):303-311.
- 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.
- Sacco JJ, Botten J, Macbeth F, Bagust A, Clark P. The average body surface area of adult cancer patients in the UK: a multicentre retrospective study. PLoS One. 2010;5(1):e8933.
- Patel N, Durland J, Awosika AO, Makaryus AN. Physiology, Cardiac Index. StatPearls. Treasure Island (FL): StatPearls Publishing; 2024.