Body Surface Area Calculator
Calculate your body surface area using three established formulas.
What Is Body Surface Area?
Body surface area (BSA) is the total surface area of the human body, typically measured in square metres (m²). It is widely used in medicine as a more accurate basis than body weight for calculating drug dosages (especially chemotherapy), cardiac output, renal function, and burns treatment.
The Three Formulas
- Du Bois: BSA = 0.007184 × height0.725 × weight0.425
- Mosteller: BSA = √(height × weight ÷ 3600)
- Haycock: BSA = 0.024265 × height0.3964 × weight0.5378
Height is in centimetres and weight in kilograms for all formulas. The Mosteller formula is the simplest and most widely used in clinical practice today.
Why BSA Matters in Medicine
BSA correlates more closely with metabolic mass and organ function than body weight alone. This makes it valuable for:
- Chemotherapy dosing: Many anticancer drugs are dosed per m² of BSA to balance efficacy and toxicity.
- Cardiac index: Cardiac output is indexed to BSA to compare across patients of different sizes.
- Renal function: Some kidney function estimates use BSA to normalise results.
- Burns assessment: The percentage of body surface affected by burns guides fluid resuscitation.
Typical BSA Values
The average BSA for an adult is about 1.7 m² for women and 1.9 m² for men. Children have much smaller BSA values, which is why paediatric dosing relies heavily on BSA calculations. Always consult a healthcare professional for medical decisions based on BSA.
Frequently Asked Questions
Body surface area (BSA) is the total surface area of the human body, measured in square metres. It is used in medicine for drug dosing, cardiac output indexing, renal function assessment, and burns treatment.
The Mosteller formula is the most widely used because it is simple and reliable. Du Bois is the original formula and is still referenced in clinical settings. Haycock is often preferred for children and infants. This calculator shows all three for comparison.
BSA correlates better with metabolic mass and organ function than body weight alone, making it a more accurate basis for dosing certain medications, especially chemotherapy and drugs with narrow therapeutic windows.