How is BSA calculated?

BSA is most commonly calculated using the Mosteller formula: BSA (m²) = √(Height (cm) × Weight (kg) / 3600). The Du Bois formula is also widely used: BSA = 0.007184 × Height^0.725 × Weight^0.425.

Why is BSA used for chemotherapy dosing?

BSA-based dosing accounts for differences in body size and metabolic rate among patients. Since cytotoxic drugs have narrow therapeutic windows, BSA helps individualize doses to maximize efficacy while minimizing toxicity.

What is a normal BSA for adults?

The average BSA for adult women is approximately 1.6 m² and for adult men approximately 1.9 m². Values vary based on height, weight, and body composition.

Is BSA the same as BMI?

No. BMI (Body Mass Index) is a ratio of weight to height squared (kg/m²) used for weight classification. BSA (Body Surface Area) estimates the total body surface in square metres and is used primarily for drug dosing and physiological indexing.

Should BSA be capped for obese patients?

Many oncology protocols cap BSA at 2.0 m² for chemotherapy dosing in obese patients. However, ASCO guidelines (2012) recommend using actual body weight for dosing. Always follow protocol-specific and institutional guidelines.

Medically Reviewed · CliniqWise Clinical Advisory Board · Updated 2026-08-27

Body Surface Area (BSA) Calculator

Calculate estimated body surface area from patient height and weight measurements using the Mosteller or Du Bois formula.

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BSA Calculator

Enter values below to calculate

Height*

Weight*

This calculator is for informational and educational purposes. Results should be interpreted with clinical judgment and local guidelines.

What is Body Surface Area (BSA)?

Body Surface Area (BSA) is a measurement of the total surface area of the human body, expressed in square metres (m²). BSA provides a more accurate reflection of metabolic mass than body weight alone and is widely used in medicine to standardize drug dosing, assess cardiac performance, and index renal function.

BSA (Mosteller) = √(Height (cm) × Weight (kg) / 3600). Average adult BSA is approximately 1.7 m².

When to Use the BSA Calculator

Chemotherapy dosing: BSA-based dosing is standard for most cytotoxic drugs to balance efficacy and toxicity.
Cardiac index calculation: Cardiac output divided by BSA provides the cardiac index (CI), a key hemodynamic parameter.
Renal function indexing: eGFR values are typically normalized to a BSA of 1.73 m².
Burn assessment: Estimating affected body surface area for fluid resuscitation calculations (e.g., Parkland formula).
Pediatric and neonatal drug dosing where body size significantly influences drug distribution and metabolism.
Calculating physiological parameters such as tidal volume, metabolic rate, and fluid requirements.
Research and clinical trials requiring standardized dosing across diverse patient populations.

Oncology drug dosingCardiac output assessmentRenal function (eGFR indexing)Burn injury managementPediatric pharmacology

BSA Formulas

Mosteller Formula (Recommended)

BSA (m²) = √(Height (cm) × Weight (kg) / 3600)

Example: √(170 cm × 70 kg / 3600) = √(3.306) = 1.818 m²

Du Bois & Du Bois Formula

BSA (m²) = 0.007184 × Height (cm)^0.725 × Weight (kg)^0.425

Example: 0.007184 × 170^0.725 × 70^0.425 = 1.813 m²

Variables

Height (cm or inches)

Standing height of the patient.

Weight (kg or lbs)

Total body weight of the patient.

The Mosteller formula is preferred in most clinical settings for its simplicity. The Du Bois formula was derived from only 9 subjects in 1916 but remains widely cited. The Haycock formula is sometimes used in pediatric patients. All formulas are approximations and may not be accurate at extremes of body size.

BSA Reference Ranges

Normal BSA varies by age, sex, and body habitus. The following values represent typical adult ranges.

Range	Classification	Health Risk
< 1.5 m²	Below Average	May need dose adjustment
1.5 – 1.7 m²	Low Normal (Women)	Standard dosing
1.7 – 1.9 m²	Average (Men)	Standard dosing
1.9 – 2.2 m²	Above Average	Dose capping may apply
> 2.2 m²	High BSA	Dose capping recommended

Many oncology protocols cap BSA at 2.0 m² for drug dosing calculations. Always follow institutional and protocol-specific guidelines.

Limitations & Clinical Warnings

BSA formulas are mathematical approximations based on height and weight. They do not account for individual variations in body composition such as muscle mass versus adipose tissue.

In obese patients, BSA formulas may overestimate metabolically active surface area, as adipose tissue is less metabolically active. This can lead to overdosing of cytotoxic chemotherapy.

Accuracy decreases at extremes of height and weight. Alternative metrics such as ideal body weight or adjusted body weight may be preferred in certain clinical scenarios.

Different electronic prescribing systems may use different BSA formulas, potentially leading to discrepancies in medication dosing. Confirm which formula your institution uses.

The Du Bois & Du Bois formula was derived from only 9 individuals in 1916, raising questions about its universal applicability to modern, diverse patient populations.

BSA-based dosing is being re-evaluated in oncology. Some newer targeted therapies and immunotherapies use flat (fixed) dosing rather than BSA-adjusted dosing.

Medical Disclaimer

This calculator is intended for use by healthcare professionals as a clinical reference tool. BSA calculations should always be verified against institutional protocols and used in conjunction with complete clinical assessment. This tool does not replace professional medical judgment.

References & Citations

Mosteller RD. “Simplified calculation of body-surface area”. New England Journal of Medicine. 1987. 317(17): 1098. DOI: 10.1056/NEJM198710223171717
Du Bois D, Du Bois EF. “A formula to estimate the approximate surface area if height and body mass be known”. Archives of Internal Medicine. 1916. 17(6_2): 863-871. DOI: 10.1001/archinte.1916.00080130010002
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(1): 62-66. PMID: 650346

Medically Reviewed

Reviewed by CliniqWise Clinical Advisory Board · Last updated: 2026-08-27 · Next review: 2027-02-27

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