BSA calculator with five published formulas
For healthcare professionals and students. Check results against your local protocols and clinical judgement; this tool does not give medical advice.
This BSA calculator works out body surface area in square metres from height and weight with the five formulas most often quoted: Mosteller, DuBois & DuBois, Haycock, Gehan & George and Boyd. Pick the one your protocol names as the headline; the others appear in a table with the percentage difference, so you can see at a glance whether the choice matters for this patient.
Body surface area is used to dose many chemotherapy drugs, to index cardiac output and other measurements, and to scale kidney function. Height can be entered in centimetres or inches and weight in kilograms, grams or pounds. It all runs in your browser.
How to use the Body Surface Area Calculator
- Enter the height and choose cm or in.
- Enter the weight and choose kg, g (useful for babies) or lb.
- Choose the headline formula your protocol uses — Mosteller is the default.
- Read the BSA, then compare the other formulas in the table.
- Check the warnings and copy the summary if you need it.
Body Surface Area Calculator features
Five formulas
Mosteller, DuBois, Haycock, Gehan-George and Boyd, all from the same height and weight.
Shows the spread
The table gives each result and how far it is from your headline formula, and warns when they differ by more than 5%.
Metric and imperial
Height in cm or inches, weight in kg, g or lb, converted with exact factors (1 in = 2.54 cm, 1 lb = 0.45359237 kg).
Working shown
The chosen formula is written out with your numbers, plus the BMI as a sense check.
Unit checks
Flags heights that look like metres, weights that look like the wrong unit, and implausible combinations.
BSA formulas
All use height in centimetres and weight in kilograms, except Boyd, which uses weight in grams. Results are in m².
| Formula | Equation | Source |
|---|---|---|
| Mosteller | BSA = √(height × weight ÷ 3600) | Mosteller RD, N Engl J Med 1987;317:1098 |
| DuBois & DuBois | BSA = 0.007184 × W^0.425 × H^0.725 | Du Bois D, Du Bois EF, Arch Intern Med 1916;17:863 |
| Haycock | BSA = 0.024265 × W^0.5378 × H^0.3964 | Haycock GB, Schwartz GJ, Wisotsky DH, J Pediatr 1978;93:62–66 |
| Gehan & George | BSA = 0.0235 × W^0.51456 × H^0.42246 | Gehan EA, George SL, Cancer Chemother Rep 1970;54:225–235 |
| Boyd | BSA = 0.0003207 × H^0.3 × W(g)^(0.7285 − 0.0188 × log₁₀ W(g)) | Boyd E, The Growth of the Surface Area of the Human Body, 1935 |
Worked example
For an adult 170 cm tall weighing 70 kg, Mosteller gives √(170 × 70 ÷ 3600) = √3.3056 = 1.82 m². The other formulas give 1.81 (DuBois), 1.83 (Haycock), 1.83 (Gehan-George) and 1.83 m² (Boyd) — within about 1.5% of each other.
For a newborn 50 cm long weighing 3,500 g the spread is far wider: 0.21 m² by DuBois against 0.23 m² by Gehan-George, a difference of about 12%. DuBois gives the lowest value at this size, while Haycock’s formula was explicitly validated in infants, children and adults. These figures are hand-calculated from the published equations and are checked by the tool’s self-test.
Which BSA formula should you use?
Use the one your protocol, trial or drug reference specifies, and keep to it for the same patient. Mosteller was proposed in 1987 as a simpler way to compute BSA with a pocket calculator and is widely used in oncology and on hospital systems; DuBois, from 1916, is the classic reference in physiology and is still widely used; Haycock is common in paediatrics.
This calculator does not apply any cap or adjusted weight. Whether to dose on actual weight, cap the BSA or adjust for obesity is a clinical and protocol decision. For kidney function scaled to 1.73 m², see the eGFR calculator.
Body Surface Area Calculator FAQ
How do I calculate body surface area?
The simplest formula is Mosteller: multiply height in cm by weight in kg, divide by 3,600 and take the square root. 170 cm and 70 kg give √3.306 = 1.82 m². The BSA calculator above does it with four other formulas too.
What is the DuBois BSA formula?
BSA = 0.007184 × weight^0.425 × height^0.725, with weight in kg and height in cm. Choose DuBois as the headline formula to make it the main result.
What is a normal body surface area?
There is no normal value as such — it depends on height and weight. The 1.73 m² used to index eGFR comes from an average adult surface area used in kidney clearance studies in the late 1920s, and many adults today are larger.
Which BSA formula is used for children?
Mosteller and Haycock are commonly used in paediatrics; Haycock’s was validated in infants, children and adults. Enter weight in grams for a baby.
Can I enter height in feet and inches?
Enter the total in inches (5 ft 7 in = 67 in) and choose in. The tool converts with 1 in = 2.54 cm.
Is BSA the same as BMI?
No. BMI is weight divided by height squared (kg/m²) and describes build; BSA estimates skin surface in m². The BMI calculator covers BMI.