Body Surface Area Calculator
Six BSA formulas · Step by step · mg/m² dose
📐 Enter height and weight to see your body surface area from six formulas, with the working and an optional mg/m² dose.
What Is Body Surface Area?
Body surface area (BSA) is the total area of the outer surface of the body, measured in square meters (m²). It cannot be measured easily, so it is estimated from height and weight using published formulas. This calculator runs six of them at once and shows how closely they agree.
BSA is used to dose most chemotherapy drugs, to index cardiac output, and to convert an indexed eGFR in mL/min/1.73 m² into an absolute value in mL/min. Redlarski and colleagues list further uses in transplant medicine, burn care, and toxicology, and note the FDA recommends BSA scaling to convert animal study doses into safe starting doses for first human trials.
In a study of 3,613 adults receiving chemotherapy at three UK centers, mean BSA was 1.91 m² for men, 1.71 m² for women, and 1.79 m² overall.
BSA Formulas With Worked Examples
All examples use a person 180 cm tall weighing 80 kg.
To convert, multiply pounds by 0.4536 for kilograms and inches by 2.54 for centimeters. 5 ft 11 in is 71 in, or 180.3 cm.
BSA Chart by Height and Weight
Body surface area in m² from the Mosteller formula.
| Height | 50 kg | 60 kg | 70 kg | 80 kg | 90 kg | 100 kg |
|---|---|---|---|---|---|---|
| 150 cm (4'11") | 1.44 | 1.58 | 1.71 | 1.83 | 1.94 | 2.04 |
| 160 cm (5'3") | 1.49 | 1.63 | 1.76 | 1.89 | 2.00 | 2.11 |
| 170 cm (5'7") | 1.54 | 1.68 | 1.82 | 1.94 | 2.06 | 2.17 |
| 180 cm (5'11") | 1.58 | 1.73 | 1.87 | 2.00 | 2.12 | 2.24 |
| 190 cm (6'3") | 1.62 | 1.78 | 1.92 | 2.05 | 2.18 | 2.30 |
50 kg is 110 lb, 70 kg is 154 lb, 80 kg is 176 lb, and 100 kg is 220 lb. BSA rises with the square root of weight, so doubling weight raises BSA by about 41 percent, not 100 percent.
Which BSA Formula Is Most Accurate?
| Formula | Equation | Notes |
|---|---|---|
| Du Bois (1916) | 0.007184 × W^0.425 × H^0.725 | Most widely used; derived from 9 subjects |
| Boyd (1935) | 0.0003207 × H^0.3 × (1000W)^(0.7285 − 0.0188 log10 1000W) | Weight in grams inside the exponent |
| Gehan and George (1970) | 0.0235 × W^0.51456 × H^0.42246 | Published in Cancer Chemotherapy Reports |
| Haycock (1978) | 0.024265 × W^0.5378 × H^0.3964 | Validated in infants, children, and adults |
| Mosteller (1987) | √(H × W ÷ 3600) | Simplest; easy on a calculator |
| Schlich (2010) | Men 0.000579479 × W^0.38 × H^1.24; women 0.000975482 × W^0.46 × H^1.08 | Separate equations by sex; adults only |
For an average adult the classic formulas agree within a few hundredths of a square meter. They spread apart at the extremes. At 175 cm and 120 kg, Mosteller gives 2.42 m², Du Bois 2.32, Boyd 2.48, and Schlich (male) 2.16.
Verbraecken and colleagues compared formulas in 1,868 adults and found all correlated at 0.97 or higher, but Du Bois underestimated BSA in obese patients by about 3 percent in men and 5 percent in women. They recommended Mosteller for its simplicity. Redlarski and colleagues compared 25 formulas and found differences of up to 0.5 m² for a standard adult physique.
BSA Dose Calculation
The choice of formula changes the dose, which is why protocols name one. The American Society of Clinical Oncology recommends full weight based chemotherapy doses for obese patients, particularly when the goal is cure, and reports that up to 40 percent of obese patients receive limited doses not based on actual body weight.
BSA adjusted eGFR
The National Kidney Foundation notes that staging uses the indexed value, while drug dosing decisions generally use the BSA adjusted value. See the GFR calculator.
BSA for Children and by Sex
Children use the same inputs. Haycock was validated in infants, children, and adults, and Mosteller is also common in pediatrics. A child 110 cm tall weighing 19 kg has a BSA of 0.76 m² by both formulas.
Schlich was developed in adults and gives about 0.60 m² for the same child, far below the others, so this calculator excludes it below 140 cm or 35 kg.
| Group | Mean BSA |
|---|---|
| Adult men (UK chemotherapy study) | 1.91 m² |
| Adult women (UK chemotherapy study) | 1.71 m² |
| All adults (same study) | 1.79 m² |
| eGFR reference size | 1.73 m² |
Men have a higher average BSA because they are taller and heavier on average. At the same height and weight the five classic formulas give the same value for men and women.
Accuracy and Limitations
- All formulas are estimates. They were fitted to small or specific groups, and Du Bois to only 9 people.
- Body shape matters. Differences grow with obesity, very low weight, and in children, where Redlarski and colleagues warn errors may matter most.
- Amputation and edema. Height and weight no longer describe the body the formula assumes.
- Not a burn chart. Burn extent is a percentage of total BSA estimated from body region charts, not from these formulas.
Common Mistakes
- Pounds in a kilogram formula. 176 entered as kg instead of lb gives 2.97 m² instead of 2.00.
- Inches as centimeters. Always convert height to cm first.
- Switching formulas between visits. A change from Du Bois to Mosteller can shift BSA by several percent with no change in the patient.
- Old weights. Recalculate BSA when weight changes, since dose follows BSA.
- Grams in Boyd. Boyd uses weight in grams inside the exponent; the other formulas use kilograms.
Frequently Asked Questions
Sources & References
- Du Bois D, Du Bois EF. Clinical calorimetry, tenth paper: a formula to estimate the approximate surface area if height and weight be known. Arch Intern Med 1916;17:863. doi.org
- Mosteller RD. Simplified calculation of body surface area. N Engl J Med 1987;317:1098. doi.org
- Haycock GB, Schwartz GJ, Wisotsky DH. Geometric method for measuring body surface area. J Pediatr 1978;93:62 to 66. doi.org
- Redlarski G, Palkowski A, Krawczuk M. Body surface area formulae: an alarming ambiguity. Sci Rep 2016;6:27966 (equations for Gehan and George, Boyd, Schlich). doi.org
- Verbraecken J, et al. Body surface area in normal weight, overweight, and obese adults. Metabolism 2006;55:515 to 524. doi.org
- Sacco JJ, et al. The average body surface area of adult cancer patients in the UK. PLoS One 2010;5:e8933. doi.org
- Griggs JJ, et al. Appropriate chemotherapy dosing for obese adult patients with cancer: ASCO guideline. J Clin Oncol 2012;30:1553 to 1561. doi.org
- National Kidney Foundation, eGFR Calculator (BSA adjusted eGFR). kidney.org
Results are for informational purposes only and should not be used as a diagnosis, prescription, or substitute for professional medical advice. Reference data reviewed: 2026.