Mosteller BSA Calculator
Use this calculator to estimate body surface area (BSA) with the Mosteller formula.
This tool is for educational use and does not replace clinical judgment.
What is body surface area (BSA)?
Body surface area (BSA) is an estimate of the total external area of the human body, usually expressed in square meters (m²). In healthcare, BSA is commonly used to guide medication dosing, especially for chemotherapy and certain IV drugs, and to help estimate physiological needs in specialized settings.
Why use the Mosteller formula?
The Mosteller method is one of the most popular BSA formulas because it is simple, fast, and sufficiently accurate for routine clinical use. It only requires height and weight and avoids the more complex exponents found in older equations.
- Easy to calculate by hand or with a calculator
- Widely recognized in medical education and practice
- Good practical balance of convenience and reliability
Mosteller formula explained
The equation is:
BSA (m²) = √((Height cm × Weight kg) / 3600)
In plain terms, multiply height by weight, divide by 3600, and then take the square root of that value.
Example calculation
For a person who is 170 cm tall and weighs 65 kg:
- 170 × 65 = 11050
- 11050 / 3600 = 3.0694
- √3.0694 ≈ 1.752
Estimated BSA = 1.75 m² (rounded).
BSA vs BMI: what’s the difference?
BSA and BMI both use height and weight, but they answer different questions:
- BSA: surface area estimate, often used for medication dosing and clinical calculations.
- BMI: weight-for-height index, often used for population-level screening of weight categories.
A healthy BMI does not automatically mean a specific BSA target, and vice versa.
Where BSA is used in practice
1) Medication dosing
Some drugs are prescribed in mg/m². This approach can help standardize dosing across different body sizes.
2) Oncology
Chemotherapy regimens frequently use BSA-based dosing. In oncology, dose decisions may still be adjusted for organ function, toxicity history, treatment protocol, and clinician judgment.
3) Burn care and critical care
BSA can contribute to broader clinical assessment models when evaluating fluid needs and treatment plans.
Tips for accurate results
- Measure height and weight as accurately as possible.
- Use the same unit system consistently (metric or imperial).
- Recalculate when there is a meaningful weight change.
- Remember that formulas provide estimates, not exact physiologic measurements.
Important limitations
BSA formulas were designed for practical estimation. They may be less representative in certain populations, including extremes of body size, edema states, or unusual body proportions. Clinical teams may choose adjusted strategies when needed.
Quick FAQ
Is Mosteller better than all other formulas?
Not necessarily “better” in every context, but it is one of the most practical and widely used options.
Can I use this for children?
The formula can be applied across age groups, but pediatric dosing should always follow clinician guidance and institutional protocols.
Should I self-dose medication with this calculator?
No. Use it for learning and estimation only. Medication decisions must come from qualified medical professionals.