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Body Surface Area (BSA) Calculator
Enter height and weight to calculate body surface area in square metres using the Mosteller, Du Bois and Haycock formulas, and compare them. BSA is a reference measure used in medicine, not a personal health score.
What body surface area is used for
Body surface area (BSA) estimates the area of the skin in square metres. A typical adult has a BSA of about 1.6 to 2.0 m². Because many physiological quantities scale with body size more closely than with weight alone, BSA is used to index measurements: cardiac output divided by BSA gives the cardiac index, and kidney filtration is reported per 1.73 m², the average adult BSA that underlies the eGFR results shown on the GFR calculator. It also appears in burn assessments and in the dosing of some drugs, especially in cancer treatment.
BSA is not a measure of health or fitness. It tells you roughly how big a body is, nothing about its composition.
The three formulas
| Formula | Equation (W in kg, H in cm) |
|---|---|
| Mosteller (1987) | √(H × W ÷ 3600) |
| Du Bois and Du Bois (1916) | 0.007184 × W0.425 × H0.725 |
| Haycock (1978) | 0.024265 × W0.5378 × H0.3964 |
For 180 cm and 80 kg, Mosteller gives exactly 2.00 m² since 180 × 80 ÷ 3600 = 4. Du Bois gives about 2.00 and Haycock about 2.01, so the formulas agree within a percent or so for typical adults. Du Bois was derived from nine people and Haycock from a group that included infants and children, which is why Haycock is often chosen for paediatric work. Mosteller is the easiest to compute by hand and is widely used in oncology.
When the formulas differ
Agreement is good in the middle of the range and weaker at the extremes. In very small children, in people with very large body weight, or in people with extreme height, the three results can differ by several percent. Which formula a hospital or protocol uses matters in dosing, so a calculator result here should not be swapped in for the figure your care team uses. Where precision matters, use the formula named by the protocol and the measured height and weight from the clinic.
- Enter your height without shoes and weight in light clothing.
- Imperial inputs are converted with 1 inch = 2.54 cm and 1 lb = 0.45359237 kg.
- Capped dosing, such as limiting BSA to 2.0 m², is a clinical policy and is not applied here.
Limits and safety
Never use this page to calculate or change a medicine dose. Dosing depends on the drug, kidney and liver function, local protocols and checks by a pharmacist or physician. BSA also loses accuracy in amputees, in people with oedema or ascites, and in very high or low body fat, because the formulas assume typical proportions. This page is educational and not medical advice.
Worked example
An adult 180 cm tall weighing 80 kg.
Inputs
| Units | Metric (cm, kg) |
|---|---|
| Height | 180 |
| Weight | 80 |
Result
Du Bois gives 2.00 m² and Haycock 2.01 m² for the same body.
| Mosteller | 2.000 m² |
|---|---|
| Du Bois and Du Bois | 1.996 m² |
| Haycock | 2.007 m² |
| Average of the three | 2.001 m² |
| Inputs in metric | 180.0 cm and 80.0 kg |
- Mosteller: square root of (height in cm x weight in kg / 3600). Du Bois: 0.007184 x W^0.425 x H^0.725. Haycock: 0.024265 x W^0.5378 x H^0.3964.
Medical disclaimer: This tool is for education and general planning. It is not medical advice and does not diagnose any condition. If you are pregnant, under 18, have an eating-disorder history or a medical condition, speak to a doctor or registered dietitian before changing your diet or exercise.
Frequently asked questions
What is a normal body surface area?
Average adults have a BSA of about 1.6 to 2.0 square metres, with the figure usually around 1.9 for men and 1.6 for women. It rises with height and weight, so there is no single healthy value.
Which BSA formula is the most accurate?
The formulas agree within a few percent in typical adults. Du Bois is the oldest, Mosteller the simplest and Haycock was designed to include children. No single formula is best for everyone.
How do I calculate BSA by hand?
With Mosteller, multiply height in centimetres by weight in kilograms, divide by 3600 and take the square root. For 170 cm and 70 kg that is the square root of 3.3056, or 1.82 m².
Why is BSA used for chemotherapy dosing?
Doses were historically scaled to body size to bring drug exposure closer between people. Today practice varies by drug and some regimens use fixed doses, so protocols decide.
Can I use this for a baby?
The formulas can be calculated for a child, but doctors usually choose the formula and rely on measured length and weight. Haycock was developed with young patients in mind.
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References and sources
- Mosteller RD (1987). Simplified calculation of body-surface area. New England Journal of Medicine 317(17):1098.
- Du Bois D, Du Bois EF (1916). A formula to estimate the approximate surface area if height and weight be known. Archives of Internal Medicine 17:863-871.
- Haycock GB, Schwartz GJ, Wisotsky DH (1978). Geometric method for measuring body surface area: a height-weight formula validated in infants, children, and adults. Journal of Pediatrics 93(1):62-66.