BSA Calculator (Body Surface Area)

Calculate your Body Surface Area using the Mosteller, Du Bois, or Haycock formula. This tool processes all data locally in your browser. No information is ever sent to any server. Completely free, no registration required.

How to Use the BSA Calculator (Body Surface Area)

1. Enter your input values above
2. Results update automatically
3. Copy or download the output

What is a BSA Calculator (Body Surface Area)?

A BSA (Body Surface Area) Calculator estimates the total surface area of the human body — a critical metric in medicine for calculating chemotherapy drug dosages, burn assessment (the 'Rule of Nines' uses BSA), fluid resuscitation, and metabolic rate estimation. Unlike BMI, BSA accounts for both height and weight in a way that correlates well with physiological parameters like blood volume and cardiac output. The Mosteller formula (the simplest and most widely used) calculates BSA from just height and weight.

How Does It Work?

Enter height and weight in metric or imperial units. The calculator applies multiple validated formulas: Mosteller (√[height(cm) × weight(kg) / 3600]), Du Bois & Du Bois (the oldest, still widely referenced), Haycock (better for infants and children), Gehan & George, and Boyd. The Mosteller result is displayed as the primary output with the range across formulas shown for context. Reference: average adult BSA is about 1.6-1.9 m² for men, 1.5-1.7 m² for women.

Formula

Mosteller: BSA (m²) = √[height(cm) × weight(kg) ÷ 3600]\n\nDu Bois: BSA (m²) = 0.007184 × height(cm)^0.725 × weight(kg)^0.425\n\nHaycock: BSA (m²) = 0.024265 × height(cm)^0.3964 × weight(kg)^0.5378\n\nGehan & George: BSA (m²) = 0.0235 × height(cm)^0.42246 × weight(kg)^0.51456\n\nAverage Adult BSA: ~1.7 m²\n\nChemotherapy Dosing: Dose = BSA × Dose per m²

Who Uses This Tool?

• Oncologists calculating chemotherapy doses based on BSA (mg/m²)
• Burn unit teams estimating burn percentage for fluid resuscitation
• Cardiologists indexing cardiac output to body size (cardiac index)
• Nephrologists calculating glomerular filtration rate (GFR) corrected for BSA
• Nutritionists estimating resting metabolic rate from body surface area

Pro Tips

• Mosteller is the preferred formula for most clinical use — it's simple, accurate within 1-2% of more complex formulas, and has the lowest calculation error risk
• BSA-based drug dosing can result in 30%+ variation in drug exposure between patients. Newer approaches (pharmacogenetic dosing) are being developed
• BSA is a better metabolic scaling factor than body weight alone. Many physiological parameters (cardiac output, GFR, metabolic rate) scale more closely with BSA than with weight
• For burn assessment: the 'Rule of Nines' divides the body into 9% sections. Use our calculator to know BSA, then calculate burn extent

Frequently Asked Questions about BSA Calculator (Body Surface Area)

Why is BSA used for chemotherapy dosing?

BSA correlates with blood volume, liver size, and kidney function — key determinants of how drugs are distributed and cleared. BSA-based dosing aims to standardize drug exposure across patients of different sizes. It's imperfect but better than flat dosing for most chemotherapeutics.

What's a normal BSA?

The average adult BSA is ~1.7 m² (men ~1.9, women ~1.6). Range for most adults is 1.4-2.2 m². Values below 1.3 or above 2.3 are unusual and should be double-checked.

Free online BSA Calculator (Body Surface Area) — no signup, 100% client-side processing. All data stays in your browser.