Body Surface Area Calculator

What is Body Surface Area (BSA)?

Body Surface Area (BSA) is the total surface area of the human body. It is a measurement used in many medical tasks, including calculating drug dosages (especially chemotherapy), assessing burn severity, determining cardiac index, and evaluating metabolic mass. BSA is often preferred over body weight for these calculations because it is a more accurate indicator of metabolic mass.

Direct measurement of BSA is difficult and impractical. As a result, several mathematical formulas have been developed over the years to estimate BSA based on a person's weight and height. This calculator provides results from eight of the most commonly used BSA formulas, making it easy to compare them.

How BSA Is Used in Medicine

BSA is a critical metric in clinical settings. Chemotherapy dosing is frequently determined using a patient's BSA to ensure the right amount of medication is administered. The cardiac index, which relates heart performance to body size, also relies on BSA. Additionally, BSA is used to estimate the extent of burns and to calculate glomerular filtration rate (GFR) for kidney function assessment.

While BSA-based dosing is widely used, there is some debate about its accuracy for drugs with a narrow therapeutic index. At the extremes of height and weight, BMI may sometimes be a better measure. Nonetheless, BSA remains a standard tool in healthcare.

The BSA Formulas Used in This Calculator

Du Bois Formula

BSA = 0.007184 × W^0.425 × H^0.725

The Du Bois formula is the most widely used BSA formula. It was developed in 1916 and remains a standard reference.

Mosteller Formula

BSA = 0.016667 × W^0.5 × H^0.5

A simplified formula that is easy to remember and commonly used in clinical practice.

Haycock Formula

BSA = 0.024265 × W^0.5378 × H^0.3964

Validated for use in infants, children, and adults.

Gehan and George Formula

BSA = 0.0235 × W^0.51456 × H^0.42246

Developed from a large sample of direct BSA measurements.

Boyd Formula

BSA = 0.03330 × W^{(0.6157 - 0.0188 × log₁₀(W))} × H^0.3

A more complex formula that uses a logarithmic component for weight.

Fujimoto Formula

BSA = 0.008883 × W^0.444 × H^0.663

Developed specifically for the Japanese population.

Takahira Formula

BSA = 0.007241 × W^0.425 × H^0.725

Similar to Du Bois but adjusted for different populations.

Schlich Formula

Women: BSA = 0.000975482 × W^0.46 × H^1.08

Men: BSA = 0.000579479 × W^0.38 × H^1.24

Uses separate equations for men and women based on 3D body scan data.

How to Use This Calculator

Select your gender and preferred unit system (metric or imperial). Enter your weight and height. The calculator will automatically compute your BSA using all eight formulas and display the results in a comparison table. The results are updated in real time as you adjust your inputs.

Reference Table of Average BSAs

Category	BSA (ft²)	BSA (m²)
Newborn child	2.69	0.25
Two-year-old child	5.38	0.50
Ten-year-old child	12.27	1.14
Adult female	17.22	1.60
Adult male	20.45	1.90

BSA is frequently compared with other body metrics. Use our BMR Calculator to estimate your basal metabolic rate, or the Body Fat Calculator to assess body composition. For medical applications, the GFR Calculator evaluates kidney function, which also uses body size parameters.

Frequently Asked Questions

What is the most accurate BSA formula?

The Du Bois formula is the most widely used and studied BSA formula. However, the Mosteller formula is often preferred in clinical settings because it is simpler. The Schlich formula is one of the more modern formulas based on 3D body scans. No single formula is perfect for everyone, which is why this calculator shows multiple results for comparison.

Why is BSA important for chemotherapy dosing?

Chemotherapy drugs have a narrow therapeutic index, meaning the difference between an effective dose and a toxic dose is small. BSA is used to calculate the right dose because it correlates well with metabolic mass and drug distribution. However, some experts argue that BSA-based dosing has limitations and other methods may be needed for certain drugs.

What is the difference between BSA and BMI?

BMI (Body Mass Index) is a simple ratio of weight to height and is used to categorize body weight status. BSA (Body Surface Area) is an estimate of the total surface area of the body and is used for medical dosing and metabolic calculations. While BMI is calculated as weight/height², BSA formulas use more complex power functions.

Can I use this BSA calculator for children?

Yes. The Haycock formula was specifically validated for infants, children, and adults. The Du Bois and Mosteller formulas are also commonly used for pediatric patients. However, for very small infants, specialized pediatric BSA formulas may be more appropriate.

What units should I use for BSA calculation?

This calculator supports both metric (kilograms and centimeters) and imperial (pounds, feet, and inches) units. All formulas internally use kilograms and centimeters, and the calculator handles the conversion automatically. The results are always displayed in square meters (m²).

Is BSA the same as the surface area of my skin?

Yes, BSA is an estimate of the total surface area of your skin. The average adult has a BSA of about 1.7 m² (women) to 1.9 m² (men). This measurement accounts for the entire outer surface of the body, including the torso, limbs, and head.

Report