Body Surface Area (BSA) Calculator [lb/kg]

Body Surface Area, or BSA, refers to the total surface area of a person’s body. It is a clinical measurement that is often used in medicine and physiology, as it is a good indicator of the body’s energy requirements ^[1]. Calculating BSA with complete precision is not easy. That is why, multiple equations have been developed to give a close estimate. With our Body Surface Calculator, tracking your BSA can be easy and convenient.

What’s My Body Surface Area?

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Doctors often refer to an individual’s BSA over their body weight to find out more about their metabolic mass. This has various applications – from setting safe dosages based on a person’s bodily requirements to determining cardiac indices (for assessing the amount of blood pumped by the heart on a per-minute basis).

However, some pieces of research suggest that BSA might not yield very accurate results for people with extreme heights or weights (very tall or very heavy). As such, other metrics like BMI and body weight are better for clinical purposes to avoid any unwanted implications ^[2].

Many people also calculate BSA values to divulge information that can help their fitness goals. Apart from being a good indicator of metabolic mass, the metric can loosely tell you about your nutritional requirements.

With our BSA calculator, you can get precise values and know exactly the amount of surface area your body would cover.

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What is Body Surface Area?

Body Surface Area is a clinical measurement used to estimate the total surface area of a person’s body. It is a crucial parameter in various medical calculations and assessments in fields like pharmacology, cardiology, and even oncology^[3].

An individual’s BSA is expressed in the standard unit of square meters (m²) or square feet (ft²), depending on their preferences. The two important parameters used in the estimation of BSA are a person’s height and weight.

Knowing their BSA estimates can help individuals understand and work with their unique characteristics. It also allows healthcare professionals to develop personalized plans and optimal treatment pathways.

What is the Average BSA?

There is a widely accepted BSA normal range devised to let individuals know if they fall in the “average” category or are outliers.

Unlike in the case of BMI or body weight, deviating far from the center values of BSA does not necessarily imply that there is a health concern.

The normal range of BSA for people belonging to different age groups is given below:

Average Body Surface by Age

In the previous section, we gave a general overview of the normal range associated with BSA values.

However, these can vary significantly by age and gender. Here, we shall give you the average Body Surface Area based on an individual’s age and gender throughout their life spans.

The following table was created following large-scale height and weight data collected by the U.S. NCHS National Health and Nutrition Examination Survey conducted between 2011 and 2014^[4].

Average BSA by Age for Males

Generally, men tend to have higher BSA values at a certain age compared to their female counterparts.

Average BSA by Age for Females

What Does Body Surface Area Tell You?

In basic words, Body Surface Area provides a measurement of the total external surface area of a person’s body, expressed in square meters or square feet. While it is not a versatile fitness indicator like BMI, it has many clinical applications in physiology and overall health.

Primarily, doctors use a patient’s BSA values to determine appropriate drug dosages for certain medications, mostly in oncology. Chemotherapy drugs and other similar agents are also largely based on a person’s BSA to account for variations in drug metabolism and distribution.

Similarly, BSA is also used to calculate an individual’s cardiac output. This ultimately helps in assessing the cardiac index, which can then be standardized and compared with the cardiac performance among individuals of different sizes.

In some cases, BSA may even be used to assess an individual’s nutritional assessment. Many scientists believe that the metric is a good indicator of the body’s unique energy requirements. Based on that, a specific nutritional plan can be devised to meet all those requirements.

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How to Calculate Body Surface Area?

Calculating one’s Body Surface Area precisely is not an easy task. There is no singular formula that can provide results with complete accuracy. That is why multiple equations have been devised for the same.

To keep things convenient, you can simply use our BSA calculator, which makes use of multiple formulas to give accurate estimates. All you need to do is input your gender, height, and weight on our BSA calculator to see your results.

We don’t use any one body surface formula. Instead, we use multiple equations to help you get a precise average.

Body Surface Area Formulas

As we have mentioned, there are multiple equations that can help you calculate your BSA ^[5]. For our calculator, we have used the most popular ones like the Du Bois formula, the Haycock formula, the Gehan and George formula, the Boyd formula, the Fujimoto formula, the Takahira formula, and the Schlich formula.

While our calculator is designed to work for both metric and imperial units of measurement, the formulas given below only provide accurate results for calculations in metric units.

All the equations and their respective formulas are given below:

Du Bois formula

BSA = 0.007184 × W^0.425 × H^0.725

Mosteller formula

BSA =  0.016667 × W^0.5 × H^0.5

Haycock formula

BSA = 0.024265 × W^0.5378 × H^0.3964

Gehan and George formula:

BSA = 0.0235 × W^0.51456 × H^0.42246

Boyd formula

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

Fujimoto formula

BSA = 0.008883 × W^0.444 × H^0.663

Takahira formula

BSA = 0.007241 × W^0.425 × H^0.725

Schlich formula

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

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

Winding Up

The Body Surface Area (BSA) is not a popular fitness or health metric. However, it has its own advantages. It is superior in terms of clinical applications like determining drug dosages or calculating cardiac output.

It can also be used to caliber one’s diet plans according to their energy and bodily requirements. With our calculator, you can easily get an accurate estimate and work accordingly.

References

1. Flint, B. (2023, March 25). Body surface area. StatPearls – NCBI Bookshelf. https://www.ncbi.nlm.nih.gov/books/NBK559005/
2. Vriesendorp, M. D., Groenwold, R. H. H., Herrmann, H. C., Head, S. J., De Lind Van Wijngaarden, R. A., Vriesendorp, P. A., Kappetein, A. P., & Klautz, R. J. (2021). The clinical implications of body surface area as a poor proxy for cardiac output. Structural Heart, 5(6), 582–587. https://doi.org/10.1080/24748706.2021.1968089
3. Body surface area. (2024, January 1). PubMed. https://pubmed.ncbi.nlm.nih.gov/32644431/
4. National health and nutrition examination survey. (2023, September 26). Centers for Disease Control and Prevention. https://www.cdc.gov/nchs/nhanes/index.htm
5. Looney, D. P., Potter, A. W., Arcidiacono, D. M., Santee, W. R., & Friedl, K. E. (2022). Body surface area equations for physically active men and women. American Journal of Human Biology, 35(2). https://doi.org/10.1002/ajhb.23823