BSA and BMI

Estimation of body surface area and calculation of BMI – preparative page for educational slides designed for medical practice, with some chunk of theory introduction.

This page is created paralell with this Czech one: cs: Odhad tělesného povrchu a výpočet BMI

References

Theory

Weight and height

The basic information about the human body is:

• the body mass
• the body height

Both values are obtained directly by weighting and measuring the human body.

SI Units

• 1 m = 1 meter = basic unit of length → used for body height too
• 1 kg = 1 kilogramm = basic unit of mass → used for body mass, too

Body surface area

Measuring of the body surface is very difficult task and therefore some attempts were done to estimate it's value. There are many formulas for calculation. One of them is the Dubois & Dubois formula:

BSA = 71,84 * m^0.425 * h ^0.725 where:

• m = body mass [kg]
• h = body height [cm]
• units of BSA = cm²

This surface can be calculated as well by means of specialised nomogram.

BMI

Body mass index is defined as the fraction of the body mass divided by square power of body height:

BMI = m / h²

where:

• m = body mass [kg]
• h = body height [m]
• units of BMI = kg/m²

Practice

Devices

• weighing scale
• measuring scale
• calculator
• nomogram Dubois & Dubois
• ruler

Task

1. Take the height and weight of the examined subject.
2. Fill measured values into the form
3. Calculate the BSA using the Dubois & Dubois formula
4. Calculate the BSA using the nomogram
5. Compare both values
6. Calculate the BMI
7. Discuss the results of measurement, compare it with the norm, compare values between the members of your group, make conclusion.