Body Surface Area (BSA) Calculator
Calculation Results
| Formula | BSA (m²) | BSA (ft²) |
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Formula Comparison
What Is Body Surface Area (BSA)?
Body Surface Area (BSA) is the total surface area of the human body. While it may seem like an abstract measurement, it serves as a crucial metabolic indicator in medicine. Unlike body weight, which can be skewed by non-metabolically active tissue like excess fat, BSA provides a more reliable measure of metabolic mass. This makes it a superior metric for determining dosages for medications that have a narrow therapeutic index, where the difference between a therapeutic dose and a toxic one is small.
Common BSA Formulas Explained
Several formulas have been developed over the past century to estimate BSA from a patient's height and weight. This calculator implements five of the most recognized methods:
Mosteller Formula
Published in 1987, the Mosteller formula is prized for its mathematical simplicity and accuracy, making it the most widely used formula in clinical practice today, especially for adults. Formula: BSA (m²) = sqrt( [height(cm) * weight(kg)] / 3600 ).
DuBois & DuBois Formula
One of the earliest formulas (1916), it was derived from direct measurements of only nine subjects. While historically significant, it is known to slightly overestimate BSA in obese individuals. Formula: BSA (m²) = 0.007184 × weight(kg)^0.425 × height(cm)^0.725.
Haycock Formula
Developed in 1978 based on data from infants and children, the Haycock formula is often considered more accurate for pediatric patients. Formula: BSA (m²) = 0.024265 × weight(kg)^0.5378 × height(cm)^0.3964.
Gehan & George Formula
This formula was created in 1970 and is another well-regarded option, often showing results similar to other modern formulas. Formula: BSA (m²) = 0.0235 × weight(kg)^0.51456 × height(cm)^0.42246.
Boyd Formula
The Boyd formula (1935) is more mathematically complex, using a logarithmic function to adjust for weight. It's less commonly used in daily practice but is valuable for comprehensive analysis. Formula: BSA (m²) = 0.0003207 × weight(grams)^(0.7285 − 0.0188*log10(weight(grams))) × height(cm)^0.3.
How BSA Is Used in Medicine
The primary application of BSA is in calculating drug dosages. By dosing based on surface area rather than just weight, clinicians can better account for differences in metabolism and drug distribution, which is especially critical in:
- Oncology: The majority of chemotherapy drugs are dosed in mg/m². BSA-based dosing helps standardize treatment and mitigate severe toxicity.
- Nephrology: Kidney function, measured as GFR, is often "normalized" by indexing it to a standard BSA of 1.73 m², allowing for meaningful comparisons between patients of different sizes.
- Cardiology: The Cardiac Index (CI), a vital measure of heart performance, is calculated by dividing the cardiac output by the patient's BSA.
Which Formula Should I Use?
The choice of formula often depends on institutional policy and patient population. For most adults, the Mosteller formula is the de facto standard due to its simplicity and reliability. For pediatric patients, the Haycock formula is frequently recommended. When there is uncertainty, or for academic purposes, calculating BSA with multiple formulas and considering the average can provide a robust estimate. However, for any clinical decision, especially drug dosing, it is imperative to follow local hospital protocols and consult with a qualified healthcare professional.
Frequently Asked Questions
Please see the structured data in the page header for a list of frequently asked questions and their answers, designed for search engines and assistive technologies.
