Body Surface Area Calculator

1. What is BSA?
2. Estimating Body Surface Area (BSA)
• The Du Bois & Du Bois and other BSA formulas
3. Body Surface Area by Age and Gender (Chart)
• Mean male BSA by age (table)
• Mean female BSA by age (table)
4. Body surface area applications

    What is BSA?

Body Surface Area (BSA) is a measurement of the surface area of a human body. The body is a complex figure and getting an accurate measurement of its surface is a considerable challenge. Therefore, instead of direct measurement, BSA is typically estimated using a regression-based formula. To calculate a person's body surface area requires knowing only two measurements: their weight and height.

In the early 1900s scientists 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 such studies we receive our understanding of the relationship between height (stature) and body weight (body mass).

BSA calculations are useful when determining different body characteristics such as energy expenditure. Calculating BMR, RMR (REE), RDEE, or TDEE requires an estimate of body surface area. These new estimates are then used when determining dietary and nutritional needs in fitness, sports, and healthcare.

    Estimating Body Surface Area (BSA)

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

BSA = 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 square meters, which can 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. The results are practically identical.

    The Du Bois & Du Bois and other BSA formulas

The original Du Bois & Du Bois original formula is:

BSA = 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). A discussion about their accuracy is ongoing in the medical community where BSA is often used to determine the treatment of patients. The formula used in our BSA calculator is one of the most-commonly used by medical care practitioners for determining the dose of a drug ^[3].

    Body Surface Area by Age and Gender (Chart)

The chart and the tables below show average body surface area estimates 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. Then they spread apart with males having a mean BSA 10-15% higher than females from age 16 onward. This is entirely due to gender-based differences in stature and weight as the formula itself contains no gender component.

Mean male BSA by age (table)

Mean (average) BSA for males by age

Age or age group	BSA (m2)	BSA (ft2)
Neonate (newborn)	0.243 m2	2.612 ft2
1 years	0.467 m2	5.027 ft2
2 years	0.563 m2	6.060 ft2
3 years	0.634 m2	6.824 ft2
4 years	0.712 m2	7.664 ft2
5 years	0.787 m2	8.471 ft2
6 years	0.867 m2	0.332 ft2
7 years	0.965 m2	10.387 ft2
8 years	1.050 m2	11.302 ft2
9 years	1.116 m2	12.013 ft2
10 years	1.236 m2	13.304 ft2
11 years	1.371 m2	14.757 ft2
12 years	1.435 m2	15.446 ft2
13 years	1.603 m2	17.255 ft2
14 years	1.720 m2	18.514 ft2
15 years	1.825 m2	19.644 ft2
16 years	1.886 m2	20.301 ft2
17 years	1.907 m2	20.527 ft2
18 years	1.980 m2	21.313 ft2
19 years	1.958 m2	21.076 ft2
20-29 years	2.016 m2	21.700 ft2
30-39 years	2.072 m2	22.303 ft2
40-49 years	2.081 m2	22.340 ft2
50-59 years	2.070 m2	22.281 ft2
60-69 years	2.065 m2	22.227 ft2
70-79 years	1.998 m2	21.506 ft2
80+ years	1.920 m2	20.667 ft2

Mean female BSA by age (table)

Mean (average) BSA for females by age

Age or age group	BSA m2	BSA ft2
Neonate (newborn)	0.234 m2	2.519 ft2
1 years	0.456 m2	4.908 ft2
2 years	0.540 m2	5.813 ft2
3 years	0.625 m2	6.727 ft2
4 years	0.702 m2	7.556 ft2
5 years	0.771 m2	8.299 ft2
6 years	0.862 m2	9.278 ft2
7 years	0.942 m2	10.140 ft2
8 years	1.051 m2	11.313 ft2
9 years	1.163 m2	12.518 ft2
10 years	1.245 m2	13.401 ft2
11 years	1.361 m2	14.650 ft2
12 years	1.512 m2	16.275 ft2
13 years	1.550 m2	16.684 ft2
14 years	1.621 m2	17.448 ft2
15 years	1.685 m2	18.137 ft2
16 years	1.698 m2	18.277 ft2
17 years	1.727 m2	18.589 ft2
18 years	1.726 m2	18.579 ft2
19 years	1.741 m2	18.740 ft2
20-29 years	1.790 m2	19.267 ft2
30-39 years	1.845 m2	19.859 ft2
40-49 years	1.842 m2	19.827 ft2
50-59 years	1.840 m2	19.806 ft2
60-69 years	1.804 m2	19.418 ft2
70-79 years	1.780 m2	19.160 ft2
80+ years	1.638 m2	17.631 ft2

Body surface area in square meters and square 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. The median is 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.

    Body surface area 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 which see use by fitness and sports coaches, dietologists, and physicians.

BSA is also used to determine the dose of health medications while taking account for patient size variation. It is used to estimate renal clearance, in chemotherapy dosage (a form of cancer treatment), in glucocorticoid dosage, and in the composition of the cardiac index. Several antivirals, antimicrobials, and antifungals require a dosing regimen based on their BSA ^[3]. Estimations related to organ transplantation often use body surface area as an important metric to inform the treatment of patients.