The skin is the body’s largest organ, and its surface area turns out to be a useful number in medicine. Heart output, kidney filtration, metabolic rate and the dose of certain drugs correlate more closely with surface area than with weight, because heat loss and many physiological processes depend on how much surface the body presents to the world. Surface area cannot be measured directly in practice, so clinicians estimate it from height and weight with formulas. This calculator applies four of the best known: Mosteller, DuBois and DuBois, Haycock, and Gehan and George.
The results are in square metres and can be shown in square centimetres or square feet. The calculator is educational and must not be used to set drug doses.
How to use the body surface area calculator
- Enter your height in centimetres, inches, feet or metres.
- Enter your weight in kilograms, pounds, grams or ounces.
- Compare the four estimates. They usually agree within a few percent.
- Use the unit menus to switch between m², cm² and ft².
Body surface area formulas
H is height in centimetres and W is weight in kilograms.
DuBois & DuBois: BSA = 0.007184 × W0.425 × H0.725
Haycock: BSA = 0.024265 × W0.5378 × H0.3964
Gehan & George: BSA = 0.0235 × W0.51456 × H0.42246
Sources: DuBois D, DuBois EF, A formula to estimate the approximate surface area if height and weight be known, Archives of Internal Medicine 1916;17:863–871; Gehan EA, George SL, Estimation of human body surface area from height and weight, Cancer Chemotherapy Reports 1970;54:225–235; Haycock GB, Schwartz GJ, Wisotsky DH, Geometric method for measuring body surface area: a height-weight formula validated in infants, children, and adults, Journal of Pediatrics 1978;93:62–66; Mosteller RD, Simplified calculation of body-surface area, New England Journal of Medicine 1987;317:1098.
Worked example
An adult 175 cm tall weighing 70 kg.
- Mosteller: √(175 × 70 ÷ 3600) = √3.403 = 1.845 m²
- DuBois: 0.007184 × 700.425 × 1750.725 = 1.848 m²
- Haycock: 1.847 m²
- Gehan and George: 1.854 m²
In square feet, the Mosteller value is 19.9 ft².
BSA by height and weight (Mosteller)
| Height (Mosteller, m²) | 50 kg | 60 kg | 70 kg | 80 kg | 90 kg | 100 kg |
|---|---|---|---|---|---|---|
| 150 cm | 1.44 | 1.58 | 1.71 | 1.83 | 1.94 | 2.04 |
| 160 cm | 1.49 | 1.63 | 1.76 | 1.89 | 2.00 | 2.11 |
| 170 cm | 1.54 | 1.68 | 1.82 | 1.94 | 2.06 | 2.17 |
| 180 cm | 1.58 | 1.73 | 1.87 | 2.00 | 2.12 | 2.24 |
| 190 cm | 1.62 | 1.78 | 1.92 | 2.05 | 2.18 | 2.30 |
Where BSA is used
- Cardiology. Cardiac index is cardiac output divided by BSA, which lets heart function be compared between people of different sizes.
- Oncology. Doses of some chemotherapy drugs are calculated per square metre, although practice is evolving and many centres cap BSA or use other methods.
- Kidney function. Glomerular filtration rate is often reported per 1.73 m² of BSA, the value for an average adult.
- Burns. The proportion of BSA affected guides treatment, using rules such as the rule of nines.
- Metabolism. Resting energy needs relate to surface area; see the BMR Calculator.
Cautions
All the formulas assume a typical body shape. They tend to be less accurate in people with obesity, very low body weight or unusual proportions. Differences between formulas are small compared with a real person’s variation, but in drug dosing even small differences can matter, so clinicians follow local protocols. For other weight-based measures see the Adjusted Body Weight Calculator, Ideal Weight Calculator and Lean Body Mass Calculator, and the Height Converter (ft/in ↔ cm) for unit conversion.
This page is for information only and is not medical advice. Speak to a doctor about your own health and any treatment decisions.
Sources
- DuBois D, DuBois EF. A formula to estimate the approximate surface area if height and weight be known. Arch Intern Med 1916;17:863–871.
- Gehan EA, George SL. Estimation of human body surface area from height and weight. Cancer Chemother Rep 1970;54:225–235.
- 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;93:62–66.
- Mosteller RD. Simplified calculation of body-surface area. N Engl J Med 1987;317:1098.
Frequently asked questions
What is body surface area?
Body surface area (BSA) is the total area of the skin, expressed in square metres. Doctors use it because many body functions, such as metabolic rate, blood volume and kidney function, scale better with surface area than with weight alone. The average adult has a BSA of about 1.7 m² to 1.9 m².
Which BSA formula is best?
There is no clear winner. Mosteller is the easiest and is widely used in clinical practice and cancer drug dosing. DuBois is the oldest and long considered the reference. Haycock was developed from data including infants and children, and Gehan and George from a paediatric cancer population. They agree within about 5 percent in typical adults.
Is BSA used for drug dosing?
Yes. Some chemotherapy drugs, for example, are dosed per m² of BSA, and cardiac index is cardiac output per m². Your care team will choose the formula and decide doses; do not use an online calculator to set a dose.
Do the formulas work for children?
Mosteller and Haycock are commonly applied to children. Haycock’s was derived from 81 subjects ranging from newborn infants to adults and is often preferred for small children. In children, use clinical tools designed for paediatrics.
Why do results differ slightly?
Each formula was fitted to a different group of people with a different method of measuring skin area. Differences are small compared with the uncertainty of the measurement itself.