Body Surface Area Calculator – BSA Calculation for Medical Use

Calculate your body surface area (BSA) quickly and accurately. Useful for medication dosing, chemotherapy, and clinical assessments using the Mosteller, DuBois, or Haycock formula.

Height

Unit

Weight

Unit

Formula

How to Use This BSA Calculator

Enter height and weight

Input your height and weight, selecting the appropriate units (cm/inches and kg/lbs).

Choose a calculation formula

Select from Mosteller (most common), DuBois, or Haycock formula based on your needs.

Calculate and view results

Get your body surface area in square meters for medication dosing or clinical use.

BSA Formulas Comparison

Formula	Equation	Best For
Mosteller	√(height × weight / 3600)	General clinical use, chemotherapy
DuBois & DuBois	0.007184 × h^0.725 × w^0.425	Historical standard, research
Haycock	0.024265 × h^0.3964 × w^0.5378	Pediatric patients
Gehan & George	0.0235 × h^0.42246 × w^0.51456	Alternative method
Boyd	Complex exponential formula	Research applications

Note: Mosteller is recommended for most clinical applications due to its simplicity and accuracy.

Understanding Body Surface Area

What Is BSA?

Body Surface Area (BSA) is the total surface area of the human body, measured in square meters. The average adult BSA is about 1.7 m² for men and 1.6 m² for women. BSA correlates better with metabolic rate and organ size than body weight alone.

Why BSA Matters in Medicine

BSA is used to calculate medication dosages for drugs with narrow therapeutic windows, such as chemotherapy agents and corticosteroids. It is also used to determine cardiac index, glomerular filtration rate, and fluid requirements for burn patients.

BSA vs Body Weight

Weight-based dosing can lead to overdosing in obese patients and underdosing in very thin patients. BSA accounts for both height and weight, providing a more accurate reflection of metabolic mass and organ function across different body types.

Clinical Applications of BSA

Chemotherapy dosing

Most chemotherapy drugs are dosed per m² of BSA to account for differences in drug metabolism and toxicity.

Cardiac index calculation

Cardiac output is normalized to BSA to compare heart function across patients of different sizes.

Burn treatment

Fluid resuscitation for burn patients is calculated based on percentage of BSA affected.

Kidney function (GFR)

Glomerular filtration rate is often normalized to 1.73 m² BSA for standardization.

Frequently Asked Questions

What is a normal BSA value?

Average BSA for adult men is approximately 1.9 m², and for adult women about 1.6 m². Values typically range from 1.5 to 2.2 m² for most adults. Children have lower BSA values that increase with growth.

Which BSA formula is most accurate?

Studies show all major formulas produce similar results for average-sized adults. Mosteller is preferred clinically because it is easy to calculate and remember. Haycock may be more accurate for children and infants.

Is BSA used for all medication dosing?

No. Most medications use weight-based or fixed dosing. BSA-based dosing is reserved for drugs with narrow therapeutic indices where small dosing errors could cause serious harm, such as chemotherapy and some immunosuppressants.

How is BSA measured directly?

Direct measurement uses 3D scanning or the DuBois method with paper cutouts, but these are impractical for routine use. Formulas based on height and weight provide estimates accurate enough for clinical purposes.

Does obesity affect BSA accuracy?

BSA formulas may overestimate metabolic mass in obese patients because adipose tissue has lower metabolic activity than lean tissue. Some clinicians use adjusted body weight or ideal body weight for BSA calculations in obese patients.

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