Body Surface Area Calculator
Estimate BSA with Mosteller, Du Bois, and Haycock formulas.
Inputs
Mosteller BSA
Common quick clinical estimate
Formula Comparison
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About This Calculator
Overview
Use this body surface area calculator to estimate BSA from height and weight with three common medical formulas.
When to Use It
- Prepare baseline values for dose discussions.
- Compare Mosteller and Du Bois outputs quickly.
- Track BSA change after major weight shifts.
BSA Formulas
Example
- Height: 170 cm
- Weight: 70 kg
- Mosteller BSA: 1.82 m2
Common Mistakes
- Mixing inches or pounds with cm or kg inputs.
- Switching formulas between follow-up visits.
- Using outdated height or weight measurements.
Tips & Next Steps
- Update measurements before major planning decisions.
- Use one formula consistently for trend tracking.
- Treat outputs as support values, not diagnosis.
Practical BSA Interpretation in Workflow
BSA is most useful when it is embedded in a repeatable process. Start by collecting fresh measurements under the same conditions each time, then calculate using a single formula for consistency. If teams switch formulas from one visit to another, trend interpretation becomes noisy because some variation comes from method choice rather than patient change.
In planning conversations, pair BSA with other indicators such as renal function, age, and treatment tolerability. BSA provides size normalization, but it is not a full patient-profile metric. For complex treatment plans, clinicians may adjust beyond formula output. This is why BSA should be viewed as a structured baseline rather than an automatic instruction.
When comparing formulas, focus on directional agreement instead of tiny decimal differences. If Mosteller, Du Bois, and Haycock all move upward after a weight increase, the trend signal is clear. If values diverge only in the second decimal place, operational decisions usually should not hinge on that spread alone. Consistency and clinical context dominate precision theater.
For record quality, store measurement date, unit system, selected formula, and resulting BSA value in the same note. This creates auditability for future review and reduces communication errors across care teams. High-quality documentation improves both patient safety and workflow clarity.
Related Calculators
References
FAQs
About This Calculator
Calculate body surface area (BSA) using Mosteller, DuBois, and Haycock formulas. Essential for accurate medication dosing, chemotherapy calculations, and clinical assessments in healthcare.
Frequently Asked Questions
What is BSA used for?
Body surface area is commonly used in clinical contexts for dose estimation and physiological assessment discussions.
Which formula should I choose?
Mosteller is widely used for quick estimation, while Du Bois and Haycock are often used for comparison.
Is BSA the same as BMI?
No. BMI estimates mass relative to height; BSA estimates total body area. They are different measures.
Why is body surface area used instead of body weight for chemotherapy doses?
Body surface area (BSA) became the standard for chemotherapy dosing because many physiological processes — including drug metabolism, glomerular filtration rate, cardiac output, and organ function — correlate more closely with BSA than with body weight alone. This is critical for chemotherapy agents with narrow therapeutic indices, where underdosing leads to treatment failure and overdosing causes severe toxicity. For example, doxorubicin is typically dosed at 60-75 mg/m². For a patient with a BSA of 1.75 m², the dose is 105-131 mg. If dosing were based purely on weight and the patient were obese, they might receive a dangerous overdose. Common BSA formulas include Mosteller (the simplest and most widely used in oncology), DuBois, and Haycock (preferred in pediatrics). For a 5'8" (173 cm), 165 lb (75 kg) person, Mosteller gives a BSA of approximately 1.87 m².
Which BSA formula is most accurate for clinical use?
Six BSA formulas are in common clinical use, and while they generally agree within 5-10% for average-sized adults, differences become clinically significant in pediatric patients and at the extremes of size. The DuBois & DuBois formula (1916) was the original standard. The Mosteller formula (1987) is the most commonly used in oncology today due to its simplicity. The Haycock formula is preferred in pediatrics as it performs better in neonates and infants. For a typical adult — 5'9", 170 lbs — all major formulas yield BSAs within a tight range of approximately 1.90-1.96 m². However, for a premature infant weighing 1.5 kg at 40 cm length, Mosteller gives 0.13 m² while Haycock gives 0.14 m² — a difference that translates to meaningful dose variation. The most important practice is consistency: using the same formula throughout a patient's treatment course avoids dose errors between cycles.