Body Surface Area Calculator

1. What is BSA?
2. Estimating Body Surface Area (BSA)
• Mean male BSA by age table:
• Mean female BSA by age table:
3. BSA applications

    What is BSA?

Body Surface Area (BSA) is simply a measurement of the surface area of your body. Since the body is a complex figure, making an accurate measurement of its surface is a considerable challenge. To address it, scientists in the early 1900s took measurements via melted paraffin and paper strips applied to their body. After removing the pieces, they were cut into regular shapes allowing accurate BSA calculation.

From these studies we have understanding of the relationship between height (stature) and body weight (mass) and a formula through which we can calculate a persons body surface area based in their weight and height. BSA calculations are useful when determining different body characteristics, for example energy expenditure in the form of BMR, RMR (REE), RDEE, TDEE, which are in turn used when determining dietary and nutritional needs.

    Estimating Body Surface Area (BSA)

To estimate your body surface area our BSA calculator uses the following formula^[1]:

0.20247 x height (m)^0.725 x mass (kg)^0.425

where height is in meters and mass is in kg. The result is in squared meters, which easily be converted to square feet, inches or yards as needed. Below are some average values for different age groups in graph and table form.

This is a slight variation of the DuBois & DuBois body surface area formula, derived in 1916 ^[4], modified for easier calculation with height expressed in meters instead of centimeters and the results are practically identical. The DuBois & DuBois original formula is:

0.007184 x height (cm)^0.725 x mass (kg)^0.425

There are other competing formulae derived over the years (e.g. Breitmann in 1932, Stevenson in 1937, Haycock in 1978, Schlich in 2010) and a discussion about their accuracy is ongoing in the medical community, but the formula used in our BSA calculator is one of the most-commonly used by medical practitioners ^[3].

Both the chart and the tables with average body surface area estimates are based on weight and height data from the U.S. NCHS National Health and Nutrition Examination Survey (2011-2014) ^[2].

The graph clearly shows that values for boys and girls are almost identical up to 14 years of age, when they significantly departure with males having a mean BSA 10-15% higher than females due to differences in stature and weight (there is no gender component in the formula).

Mean male BSA by age table:

Mean female BSA by age table:

Body surface area in squared meters and squared feet in the graph and tables is calculated using our body surface area calculator. It should be noted that the mean and the median values, at least for children and adolescents of age 0-20 differ significantly, with the median being significantly lower than the mean, suggesting that the distribution is affected by a relatively small number of overweight and obese individuals. Take this into account when interpreting the data.

    BSA applications

Body surface area is used to calculate the resting energy expenditure, also known as resting metabolic rate when the rate required is per square meter per hour, and not the daily rate. The same applies for total daily energy expenditure calculations.

BSA is also used to determine the dosage of medications, to estimate renal clearance, in chemotherapy dosage, glucocorticoid dosage and in the composition of the cardiac index. Several antivirals, antimicrobials, and antifungals require a dosing regimen based on the BSA ^[3]. Estimations related to organ transplantation often use the body surface area as an important metric.