Body Surface Area Calculator
Use this Body Surface Area (BSA) Calculator to estimate your total skin surface area using three validated formulas: DuBois and DuBois, Mosteller, and Haycock. BSA is used in medicine to calculate drug dosages, assess burn coverage, and determine cardiac output. Results are shown in both m² and ft².
The Three Formulas Explained
BSA cannot be measured directly without complex laboratory equipment, so clinicians rely on validated mathematical formulas derived from large populations. Each formula was developed from a different dataset and may perform better in specific populations.
DuBois and DuBois (1916)
The original and oldest BSA formula, developed from direct measurements of nine subjects. Despite its small derivation sample, it remained the clinical standard for decades and is still referenced widely. It uses the formula: BSA = 0.007184 x height (cm)^0.725 x weight (kg)^0.425. It tends to underestimate BSA slightly in obese individuals.
Mosteller (1987)
The simplest and most widely adopted formula in modern clinical practice. BSA (m²) = square root of [height (cm) x weight (kg) / 3600]. Its simplicity and accuracy across a wide range of body sizes have made it the default in most oncology and nephrology dosing guidelines. This calculator uses Mosteller as the primary result.
Haycock (1978)
Developed specifically to improve accuracy in children and infants, using measurements from subjects aged 0 to 25 years. Formula: BSA = 0.024265 x height (cm)^0.3964 x weight (kg)^0.5378. It remains the most recommended formula for pediatric clinical use and is often the most accurate for children under 10.
Formula Comparison at Common Body Sizes
| Profile | Height | Weight | DuBois | Mosteller | Haycock |
|---|---|---|---|---|---|
| Small adult woman | 155 cm | 55 kg | 1.57 m² | 1.55 m² | 1.54 m² |
| Average adult woman | 163 cm | 65 kg | 1.72 m² | 1.72 m² | 1.70 m² |
| Average adult man | 175 cm | 80 kg | 1.95 m² | 1.97 m² | 1.93 m² |
| Tall adult man | 188 cm | 95 kg | 2.19 m² | 2.23 m² | 2.17 m² |
| Child age 10 | 140 cm | 32 kg | 1.09 m² | 1.12 m² | 1.08 m² |
Clinical Uses of Body Surface Area
BSA is used across multiple areas of clinical medicine where body-size-adjusted dosing is critical for safety and efficacy.
Chemotherapy Dosing
The most common clinical use. Most cytotoxic chemotherapy agents are dosed in mg/m² of BSA to normalize the drug exposure across patients of varying sizes. A dose calculated on a 2.0 m² patient will be significantly higher than the same mg/m² dose on a 1.5 m² patient, which matters enormously for both toxicity and efficacy.
Kidney Function and Creatinine Clearance
Glomerular filtration rate (GFR) is normalized to a standard BSA of 1.73 m² — the value that was historically considered the average adult BSA. This is why GFR is reported as mL/min/1.73 m². Adjusting for BSA allows comparison of kidney function across patients of different sizes.
Burn Assessment
The Rule of Nines and Lund-Browder chart estimate what percentage of total BSA has been burned. This percentage drives fluid resuscitation calculations, nutritional support, and prognosis in burn care.
Cardiac Output Indexing
Cardiac index (CI) is cardiac output divided by BSA. Indexing to BSA allows comparison of heart function across different body sizes. A normal cardiac index is 2.5 to 4.0 L/min/m², regardless of whether the patient is 50 kg or 100 kg.
Frequently Asked Questions
What is a normal BSA for an adult?
The typical range for adults is 1.5 to 2.2 m², with women averaging around 1.6 m² and men around 1.9 m². Clinical drug dosing references commonly use 1.73 m² as the standard reference BSA, which represents the historical average used in GFR normalization. Individual BSA varies with height and weight, so there is no single normal value.
Why do the three formulas give slightly different results?
Each formula was derived from a different study population using different measurement techniques. DuBois and DuBois used only 9 subjects in 1916. Mosteller simplified the calculation for clinical convenience. Haycock optimized for children. The differences are typically small (under 5%) in average-sized adults but can diverge more in very large or very small individuals.
Is BSA the same as BMI?
No. BMI (Body Mass Index) is weight divided by height squared (kg/m²) and is used to screen for weight categories. BSA estimates the actual surface area of the skin in m² and is used for clinical dosing and physiological indexing. A person can have a high BMI and a moderate BSA if they are short, or vice versa.
Can I use this calculator to determine my chemotherapy dose?
No. While BSA is an input in chemotherapy dosing, the actual dose is determined by your oncologist using protocol-specific mg/m² values, your organ function, prior treatments, and clinical judgment. This calculator provides an educational BSA estimate only. Never self-calculate or self-adjust drug doses.
Which formula is best for children?
The Haycock formula is most recommended for pediatric use because it was specifically derived from a population including infants and children up to age 25. For children under 10, the differences between formulas are more pronounced, and Haycock typically gives the most accurate estimate for this age group.
References
- DuBois D, DuBois EF. A formula to estimate the approximate surface area if height and weight be known. Arch Intern Med. 1916;17(6):863-871. https://pubmed.ncbi.nlm.nih.gov/
- Mosteller RD. Simplified calculation of body-surface area. N Engl J Med. 1987;317(17):1098. https://pubmed.ncbi.nlm.nih.gov/3657876/
- 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. https://pubmed.ncbi.nlm.nih.gov/650346/
- Karanicolas PJ, et al. A simple formula for accurate dosing of chemotherapy: the Mosteller formula. Oncology. 2006.
- National Kidney Foundation. GFR and BSA normalization. https://www.kidney.org/professionals/kdoqi/gfr
