Body Surface Area Calculator

Mosteller is the most commonly used formula in modern oncology guidelines due to its simplicity and acceptable accuracy. Du Bois is the historical standard and is still preferred in cardiac physiology. Haycock is recommended for pediatric patients. This calculator shows all three so you can match the formula to the specific clinical protocol.

Drug distribution, clearance, and toxicity all scale with body size. Dosing per kg of body weight was found to be insufficiently precise because fat tissue has much lower drug uptake than lean tissue. BSA-based dosing approximates the volume of metabolically active body tissue better than raw weight for most cytotoxic agents.

The Rule of Nines divides the body into regions each representing approximately 9% of total BSA: head and neck (9%), each arm (9%), chest (9%), abdomen (9%), upper back (9%), lower back (9%), each thigh (9%), each lower leg (9%), and perineum (1%). A burn covering 18% BSA or more typically requires hospital admission and IV resuscitation.

BSA is an estimate of total external skin surface area. The actual skin surface is somewhat larger because it includes folds, creases, and the internal surfaces of body orifices - but BSA formulas capture the clinically relevant external surface well enough for dosing purposes. BSA should not be confused with body fat or lean mass, which are different measurements.