BSA: critical in medicine, surprising elsewhere
Body Surface Area is the gold standard for chemotherapy dosing, cardiac index, and normalised renal clearance (mL/min/1.73m²).
Du Bois (1916) is the classic. Mosteller (1987) is a fast square-root approximation widely used in clinical practice. Haycock works well in paediatrics.
Different formulas vary by ~5%, which is why drug protocols often specify which formula to use.