Body Surface Area (BSA) Calculator

Chemotherapy drugs distribute through body fluids and organs whose volume correlates better with BSA than with weight. Two patients of the same weight but different heights (and so different BSAs) need different chemo doses. The convention is to dose chemo as mg/m² × BSA — giving more consistent plasma levels across body sizes.

Average adult BSA is 1.7-1.9 m² (males slightly higher than females). A 170 cm × 70 kg adult has a BSA of ~1.82 m² by Mosteller. Very small adults (<1.5 m²) and very large adults (>2.2 m²) may need clinical dose-capping for chemotherapy, where empirical BSA caps of 2.0-2.2 m² are common to avoid over-toxicity.

Some chemotherapy protocols cap BSA at 2.0 or 2.2 m² for obese patients to prevent dose-related toxicity. The American Society of Clinical Oncology (ASCO) generally recommends using actual body weight to compute BSA (not adjusted) for full chemo doses unless specific protocol guidance says otherwise. Check the protocol — practice varies.

Each was derived from a different empirical study (DuBois from 9 patients in 1916, Mosteller from a simplified regression in 1987, etc.). For typical adult ranges they agree within ±5%. For extreme body sizes (very small babies, very large adults) the differences grow. The Mosteller is preferred because it's simple, robust, and equally accurate across most patients.