Body Surface Area Calculator
Calculate your Body Surface Area (BSA) using multiple formulas. BSA is used in clinical settings for determining medication dosages, cardiac index, and metabolic mass estimation.
What is Body Surface Area (BSA)?
Body Surface Area (BSA) is the total surface area of a human body. Direct measurement of BSA is difficult, and as such many formulas have been published that estimate BSA based on height and weight.
BSA is often used in clinical purposes over body weight because it is a more accurate indicator of metabolic mass (the body's need for energy). Metabolic mass can be estimated using fat-free mass, which includes bones, tendons, inner organs, muscles, blood, nerves, and more. Since body fat is not metabolically active, fat-free mass is a reasonable estimate of metabolic mass.
Table of Average BSAs
| Category | ft² | m² |
|---|---|---|
| Newborn child | 2.69 | 0.25 |
| Two-year-old child | 5.38 | 0.5 |
| Ten-year-old child | 12.27 | 1.14 |
| Adult female | 17.22 | 1.6 |
| Adult male | 20.45 | 1.9 |
Clinical Uses of BSA
BSA is used in various clinical settings, including:
Chemotherapy Dosages
Most commonly, BSA is used to determine dosages for chemotherapy (a category of cancer treatment). While dosing for chemotherapy is often determined using a patient's BSA, there exist arguments against the use of BSA to determine medication dosages that have a narrow therapeutic index.
Cardiac Index
BSA is used to determine cardiac index, which relates a person's heart performance to their body size. This helps healthcare professionals assess cardiovascular function relative to body size.
Metabolic Mass Estimation
BSA is a more accurate indicator of metabolic mass than body weight alone. It's particularly useful for estimating energy requirements and metabolic function.
BSA Formulas
Below are some of the most popular formulas for estimating BSA. The most widely used is the Du Bois formula, which has been shown to be effective for estimating body fat in both obese and non-obese patients, unlike body mass index.
Men: BSA = 0.000579479 × W0.38 × H1.24
Where BSA is in m², W is weight in kg, and H is height in cm
Important Limitations
While BSA is widely used, there are limitations. If the therapeutic index is too narrow, BSA may not be an accurate enough measure, and there is a risk of causing a toxic rather than therapeutic effect. There is also evidence that BSA becomes less accurate at the extremes of height and weight, and BMI may be a better estimate in such cases. Despite these limitations, the effects of chemotherapy dosages as determined by BSA measurements still remain more consistent than those determined by body weight alone.
Note: This calculator provides estimates only and should not replace professional medical advice. BSA calculations are tools to help healthcare professionals, but actual medication dosages and clinical decisions should be made by qualified healthcare providers.