Calculate your Body Surface Area (BSA) using four scientifically validated formulas — Mosteller, Du Bois, Haycock, and Boyd. BSA is a critical measurement used in medical dosing, chemotherapy calculations, cardiac output indexing, and burn severity assessment.
Average adult BSA: 1.6 - 1.9 m² (women), 1.7 - 2.1 m² (men)
Mosteller formula (highlighted above) is the most commonly used formula in clinical practice due to its simplicity and accuracy. It is recommended by the American Society of Clinical Oncology for chemotherapy dosing.
Worked examples showing BSA calculations for different patient profiles using all four formulas.
Patient: Adult male, 70 kg, 175 cm
BSA (Mosteller): √((175 × 70) / 3600) = 1.84 m²
BSA (Du Bois): 0.007184 × 70^0.425 × 175^0.725 = 1.86 m²
BSA (Haycock): 0.024265 × 70^0.5378 × 175^0.3964 = 1.84 m²
BSA (Boyd): 1.86 m²
All formulas agree closely for average-sized adults.
Patient: Child, 22 kg, 120 cm
BSA (Mosteller): √((120 × 22) / 3600) = 0.86 m²
BSA (Du Bois): 0.007184 × 22^0.425 × 120^0.725 = 0.87 m²
BSA (Haycock): 0.024265 × 22^0.5378 × 120^0.3964 = 0.86 m²
BSA (Boyd): 0.87 m²
Haycock formula is often preferred for pediatric populations.
Patient: 154 lbs, 5 ft 9 in (69 inches = 175.26 cm)
Converted: 154 lbs = 69.9 kg, 69 in = 175.3 cm
BSA (Mosteller): √((175.3 × 69.9) / 3600) = 1.84 m²
BSA (Du Bois): 0.007184 × 69.9^0.425 × 175.3^0.725 = 1.85 m²
BSA (Haycock): 0.024265 × 69.9^0.5378 × 175.3^0.3964 = 1.83 m²
The calculator handles unit conversion automatically for you.
Enter the weight and height values from any example above into the Calculator tab to verify the results yourself. Small rounding differences (< 0.01 m²) are normal. The Mosteller formula is highlighted as it is the most commonly used in clinical practice due to its simplicity.
This calculator implements four widely recognized BSA formulas. Each has unique characteristics that make it suitable for different clinical scenarios.
Source: Mosteller RD. Simplified calculation of body-surface area. N Engl J Med. 1987;317(17):1098.
Best for: General clinical use, chemotherapy dosing, and routine BSA estimation. It is the most widely used formula in clinical practice today because of its simplicity — requiring only a square root calculation. It has been validated against the Du Bois method and shows excellent agreement across most body sizes.
Source: Du Bois D, Du Bois EF. A formula to estimate the approximate surface area if height and weight be known. Arch Intern Med. 1916;17:863-871.
Best for: Adults of average body composition. This is the original BSA formula, derived by measuring 9 subjects using the mold method. Despite the small sample size, it has been extensively validated and remains widely used. It slightly underestimates BSA in obese patients and overestimates in very lean individuals.
Source: 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.
Best for: Pediatric patients, especially infants and children. The Haycock formula was developed using a larger and more diverse population including children. It has different exponent weights that more accurately reflect the body proportions of growing children. It is often the formula of choice in pediatric oncology and neonatology.
Source: Boyd E. The Growth of the Surface Area of the Human Body. University of Minnesota Press. 1935.
Best for: Comprehensive research applications and patients across a wide weight range. The Boyd formula is unique because the weight exponent is itself a function of weight, allowing the formula to adjust for different body sizes more flexibly. It provides accurate estimates across the full range from premature infants to large adults.
Different BSA formulas were developed using different populations and measurement techniques. The differences between them are typically less than 5-10% for average-sized adults, but can be more significant for children, obese patients, or very lean individuals. This calculator allows you to compare all four results to get a comprehensive picture. In clinical practice, it is common to use the same formula consistently for a given patient to ensure dosing consistency.
Follow these simple steps to calculate your Body Surface Area and understand its medical significance.
Input your current body weight. You can switch between kilograms (kg) and pounds (lbs) using the dropdown selector. The calculator will automatically convert pounds to kilograms. Weight is a key factor in BSA — larger individuals have greater surface area.
Input your height. You can switch between centimeters (cm) and feet using the dropdown selector. If using feet, enter your height in decimal feet (e.g., 5.75 for 5'9"). Height, like weight, is essential for accurate BSA estimation.
Press the calculate button to see your BSA results. The calculator will display results from all four formulas simultaneously, with the Mosteller formula highlighted as the clinical standard.
Compare results across all four formulas. For average adults, the values should be very similar (typically within 0.05 m² of each other). Larger discrepancies may occur for children, very tall individuals, or those with extreme body weights. The interpretation section provides context for your results.
Share your BSA results with your healthcare provider for proper clinical interpretation. BSA is used in chemotherapy dosing, cardiac output calculations, renal function assessment, and burn severity classification. Never use BSA results for self-medication or dosing decisions without professional medical supervision.
Body Surface Area (BSA) is the measured or calculated surface area of the human body. It has been an important clinical measurement for over a century because many physiological processes scale with body surface area rather than body weight. The first BSA formula was developed by Du Bois and Du Bois in 1916 using direct measurements of nine subjects. Since then, numerous formulas have been developed using larger and more diverse populations, but all are based on the same fundamental principle: BSA can be estimated from height and weight using power-law relationships.
The Mosteller formula, developed in 1987, simplified the calculation to a single square root operation and has become the standard in clinical practice. Its mathematical simplicity does not compromise accuracy — it shows excellent correlation with more complex formulas across most body sizes.
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Body Surface Area (BSA) is a measurement of the total surface area of the human body. Unlike simple height and weight measurements, BSA provides a two-dimensional representation of body size that correlates more closely with several physiological processes, including metabolic rate, cardiac output, glomerular filtration rate (kidney function), and drug metabolism. BSA is typically expressed in square meters (m²).
The concept of BSA was first introduced in the late 19th century when physiologists recognized that metabolic rate scales more closely with surface area than with body mass. This insight, known as the "surface area law," led to the development of the first BSA formulas. Today, BSA is an essential clinical measurement used across multiple medical specialties.
While Body Mass Index (BMI) is a simple ratio of weight to height squared (kg/m²) used to classify body weight categories, BSA is a direct estimate of the body's physical surface area. BMI is primarily used for population-level weight classification and health risk assessment. BSA, on the other hand, is used for individual-level medical calculations, particularly for drug dosing. Two individuals with the same BMI can have very different BSA values if they have different heights, which is why BSA is preferred over BMI for many clinical calculations.
The human body's surface area is approximately 1.5 to 2.0 m² for average adults. The skin, which forms the outer surface, is the largest organ in the body. BSA is closely related to: Metabolic Rate — Heat loss and energy expenditure scale with surface area; Blood Volume — Total blood volume correlates with BSA; Cardiac Output — Heart function is often indexed to BSA (cardiac index = cardiac output / BSA); Renal Function — Glomerular filtration rate (GFR) is normalized to BSA (mL/min/1.73 m²); and Drug Distribution — Many drugs, especially chemotherapeutic agents, are dosed based on BSA because it better predicts drug clearance than body weight alone.
BSA is the standard method for dosing the majority of chemotherapy drugs. Because chemotherapy agents have narrow therapeutic windows — meaning the difference between an effective dose and a toxic dose is small — accurate BSA calculation is critical for patient safety. The American Society of Clinical Oncology (ASCO) recommends BSA-based dosing for most cytotoxic agents. The Mosteller formula is the most commonly used for this purpose.
Body Surface Area is used to estimate the percentage of total body surface area affected by burns, a measurement known as Total Body Surface Area (TBSA) burned. The "Rule of Nines" is a rapid estimation method, but more precise BSA calculations are used in burn units to guide fluid resuscitation, nutritional support, and surgical planning. Accurate TBSA estimation is critical — it determines whether a patient requires transfer to a specialized burn center.
Cardiac output — the amount of blood the heart pumps per minute — varies with body size. To compare cardiac function across patients of different sizes, cardiologists use the Cardiac Index (CI), which is cardiac output divided by BSA. Normal cardiac index ranges from 2.5 to 4.0 L/min/m². This measurement is essential in critical care and during cardiac surgery.
Glomerular Filtration Rate (GFR), the standard measure of kidney function, is typically reported normalized to a BSA of 1.73 m². This normalization allows clinicians to compare kidney function across patients of different body sizes. The formula is: eGFR (corrected) = eGFR (measured) × (1.73 / patient BSA). This correction is particularly important for patients at the extremes of body size.
Many non-chemotherapy medications are also dosed based on BSA, including certain anesthetics, corticosteroids, immunosuppressants, and cardiovascular drugs. BSA-based dosing is particularly important for drugs with a narrow therapeutic index and for drugs used in pediatric populations, where weight-based dosing may be less accurate due to changing body proportions during growth.
In sports science and physiology, BSA is used to calculate physiological variables such as basal metabolic rate (BMR), total energy expenditure, and thermoregulatory capacity. The Harris-Benedict equation for BMR, for example, incorporates BSA as a variable. In environmental physiology, BSA helps predict heat exchange between the body and the environment.
Newborn: 0.20 - 0.25 m²
Infant (1 year): 0.40 - 0.50 m²
Child (5 years): 0.70 - 0.90 m²
Adolescent (15 years): 1.40 - 1.70 m²
Adult woman: 1.60 - 1.90 m²
Adult man: 1.70 - 2.10 m²
Body composition: Muscle tissue is denser than fat; two people with same weight/height can have different BSA.
Pregnancy: BSA formulas may underestimate true surface area during pregnancy.
Edema: Fluid retention can increase body dimensions without changing actual BSA.
Amputations: BSA formulas assume full body — adjustments are needed for amputees.
Extreme sizes: All formulas are less accurate at weight extremes.
⚠️ Important Medical Disclaimer: This Body Surface Area calculator is for informational and educational purposes only. BSA values are estimates based on validated formulas and may not be accurate for all individuals, particularly those at extreme ends of the weight/height spectrum, patients with amputations, edema, or unusual body shapes. BSA calculations should only be used for medical dosing under the supervision and direction of a qualified healthcare provider. Never adjust medication dosages or make medical decisions based solely on the results of this calculator. Always consult with a licensed physician, oncologist, or clinical pharmacist for proper dosing and treatment decisions.