As the name indicates, the body surface area (BSA) is the total area that covers the entire surface of the human body. This value if of great importance in medicine because the dose and dosage of drugs and the amount of fluids to be administered intravenously are usually calculated taking the BSA into consideration. Certain indices such as the glomerular filtration rate (GFR) and cardiac index are calculated in relation to the BSA.

Although there are many formulas to calculate the BSA, the ones based on the height and weight are commonly used as these are less complex and the results are more or less consistent.