Free Body Surface Area Calculator Online
Calculate your body surface area (BSA) using Du Bois, Mosteller, and Haycock formulas with this free body surface area calculator. Used in clinical settings for drug dosing and metabolic assessments — available online and free.
Body Surface Area
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BSA Formulas Explained
The body surface area calculator uses three validated formulas. The Du Bois formula (1916) is the gold standard: BSA = 0.007184 × Height^0.725 × Weight^0.425. It was derived from direct surface measurements using molds of human bodies. Despite being over a century old, it remains the most widely used formula in clinical practice.
The Mosteller formula (1987) simplified the calculation: BSA = square root of (Height × Weight / 3600). It produces nearly identical results to Du Bois and is easier to compute mentally. Many hospitals use the Mosteller formula for quick bedside calculations.
The Haycock formula (1978) is preferred for pediatric patients: BSA = 0.024265 × Height^0.3964 × Weight^0.5378. It was validated specifically for children and infants, where the body surface area calculator using adult formulas may be less accurate.
Clinical Uses of BSA
Chemotherapy Dosing
Most chemotherapy drugs are dosed per m² of body surface area. The body surface area calculator helps oncologists determine the right dose to maximize efficacy while minimizing toxicity.
Cardiac Index
Cardiac output divided by BSA gives the cardiac index — a key measure of heart function adjusted for body size. Normal is 2.5–4.0 L/min/m².
Burn Assessment
BSA is used to calculate the total body surface area affected by burns, which determines fluid resuscitation needs and treatment protocols.
Renal Clearance
Glomerular filtration rate (GFR) is often normalized to 1.73 m² BSA, which is the average adult BSA. This allows comparison across different body sizes.
BSA vs. BMI — Understanding the Difference
BMI and BSA are often confused, but they serve entirely different purposes. BMI (Body Mass Index) is a screening tool that classifies weight status using the ratio of weight to height squared. BSA (Body Surface Area) calculates the actual surface area of the body for medical dosing and metabolic calculations. A body surface area calculator and a BMI calculator answer fundamentally different questions. BMI asks "is this person at a healthy weight?" BSA asks "how much surface area does this body have?" Both are useful — but in completely different contexts. Use this free body surface area calculator when you need BSA for clinical purposes.
Frequently Asked Questions
Disclaimer: This free online body surface area calculator provides estimates based on validated formulas. For clinical drug dosing and medical decisions, always consult a healthcare professional. Do not use this calculator as a substitute for professional medical judgment.
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