Body Surface Area (BSA) Calculator

Why does oncology use BSA for chemotherapy dosing? Because many cytotoxic drugs are cleared from the body through processes that scale with surface area better than with weight — a 180 cm person with the same weight as a 160 cm person will clear a drug differently, and dosing by weight alone would lead to under- or overdosing. The BSA calculator computes your surface area from height and weight using multiple validated formulas. All medication dosing decisions require physician or pharmacist evaluation.

BSA Formulas Compared

Multiple formulas exist; each was validated in a different population:

DuBois & DuBois (1916): BSA = 0.007184 × height (cm)^0.725 × weight (kg)^0.425

Mosteller (1987): BSA = √[height (cm) × weight (kg) / 3600]

Haycock (1978): BSA = 0.024265 × height (cm)^0.3964 × weight (kg)^0.5378

Gehan & George (1970): BSA = 0.0235 × height (cm)^0.42246 × weight (kg)^0.51456

Average adult BSA: 1.7–1.9 m². The Mosteller formula is most widely used in clinical practice due to its simplicity; DuBois is the original and most historically referenced. Use this online calculator to compute BSA using all major formulas simultaneously. Always confirm dosing calculations with a qualified prescriber or clinical pharmacist.

Clinical Applications of BSA

• Chemotherapy dosing: most cytotoxic agents (doxorubicin, cisplatin, paclitaxel) are dosed in mg/m² of BSA; standard adult dose assumes BSA ≈ 1.73 m²
• Cardiac index: cardiac output normalized to BSA (normal 2.2–4.0 L/min/m²)
• Burns: rule of nines uses BSA fractions to estimate burned area for fluid resuscitation
• Glomerular filtration rate (eGFR): reported normalized to 1.73 m² BSA for comparison across body sizes
• Pediatric dosing: BSA-based dosing scales appropriately from infants through adolescents

The adjusted body weight calculator and clinical calculators provide complementary dosing support tools.

Why BSA Scales Drug Dosing Better Than Weight

Many physiological parameters — cardiac output, renal filtration, metabolic rate — scale with BSA more closely than with weight. This is because BSA reflects the functional capacity of key metabolic organs better than total mass, which includes variable amounts of fat (metabolically relatively inert for drug clearance). For chemotherapy specifically: drugs cleared by the kidneys and liver are metabolized and excreted in proportion to organ functional capacity, which correlates better with body surface area than with total body weight. However, BSA-based dosing is imperfect — it does not account for organ function, protein binding, drug transporters, or pharmacogenomic variation, which is why therapeutic drug monitoring is critical for narrow-therapeutic-index drugs. All dosing decisions require physician and pharmacist supervision.