Pediatric BSA Calculator

Calculate the body surface area (BSA) of pediatric patients using various established formulas. BSA is crucial for accurate medication dosing and fluid calculations in children.

How to Use This Calculator

Enter the child's weight and select the appropriate unit
Enter the child's height and select the appropriate unit
Choose the BSA formula you want to use (Mosteller is most commonly used)
Click Calculate to see the body surface area in square meters

Formula Used

Mosteller: BSA (m²) = √(Weight (kg) × Height (cm) / 3600)

DuBois & DuBois: BSA (m²) = 0.007184 × Weight (kg)^0.425 × Height (cm)^0.725

Haycock: BSA (m²) = 0.024265 × Weight (kg)^0.5378 × Height (cm)^0.3964

Boyd: BSA (m²) = 0.0003207 × Weight (g)^0.7285 - 0.0188 × log(Weight (g))

Where:

BSA = Body Surface Area in square meters
Weight = Child's weight in kilograms
Height = Child's height in centimeters

Example Calculation

Real-World Scenario:

A pediatrician needs to calculate the BSA of a 6-year-old child to determine the appropriate dosage of a medication that is dosed by BSA.

Given:

Weight = 22 kg
Height = 115 cm
Formula = Mosteller

Calculation:

BSA = √(22 × 115 / 3600) = √(2530 / 3600) = √0.703 = 0.839 m²

Result: The child's body surface area is 0.84 m², which can be used to calculate the appropriate medication dosage.

Why This Calculation Matters

Practical Applications

Medication dosing for chemotherapy drugs
Calculating fluid requirements for burn patients
Determining appropriate radiation therapy doses
Cardiovascular and renal function assessments

Key Benefits

More accurate dosing than weight-based calculations alone
Standardized approach across different healthcare settings
Reduces risk of medication errors in pediatric patients
Helps determine appropriate medical equipment sizes

Common Mistakes & Tips

Always ensure you're using the correct units for each formula. Most formulas require weight in kilograms and height in centimeters. Using pounds or inches without proper conversion will lead to inaccurate results.

Children have different body proportions than adults, so it's important to use pediatric-specific BSA formulas. The formulas provided in this calculator are validated for pediatric use across different age groups.

BSA calculations may be less accurate for children with atypical body composition (e.g., obesity, cachexia, amputations). In these cases, healthcare providers may need to adjust calculations or use alternative methods.

Frequently Asked Questions

The Mosteller formula is most commonly used in clinical practice due to its simplicity and reasonable accuracy across different age groups. However, for specific clinical situations, healthcare providers may prefer other formulas. Research suggests that the Haycock formula may be slightly more accurate for infants and young children.

BSA calculations can be used for children of all ages, including newborns. However, for very premature infants or extremely low birth weight infants, healthcare providers may use specialized methods or weight-based dosing instead, as BSA formulas may be less accurate in this population.

For rapidly growing infants and young children, BSA should be recalculated every 1-3 months or whenever there is a significant change in weight or height. For school-age children, recalculation every 3-6 months is typically sufficient. For long-term medications, healthcare providers will specify when BSA should be reassessed.

References & Disclaimer

Medical Disclaimer

This calculator is for educational and informational purposes only. It is not a substitute for professional medical advice, diagnosis, or treatment. Always seek the advice of a qualified healthcare provider with any questions you may have regarding a medical condition or treatment. Do not disregard professional medical advice or delay in seeking it because of something you have read or calculated on this website.

References

Mosteller RD. "Simplified Calculation of Body Surface Area." N Engl J Med. 1987;317(17):1098. - The original paper describing the simplified Mosteller formula.
Redlarski G, Palkowski A, Krawczuk M. "Body surface area formulae: an overview with hints on their use." J Pediatr Endocrinol Metab. 2016;29(7):733-741. - A comprehensive review of different BSA formulas.
Johns Hopkins Pediatric Drug Dosing Guide - Clinical guidance on using BSA for pediatric medication dosing.

Accuracy Notice

The BSA calculations provided by this calculator are estimates based on mathematical formulas. Individual variations in body composition may affect the accuracy of these calculations. These formulas should not be used for patients with significant physical abnormalities such as amputations, severe burns, or extreme obesity without appropriate adjustments by a healthcare professional.

About the Author

Kumaravel Madhavan

Web developer and data researcher creating accurate, easy-to-use calculators across health, finance, education, and construction and more. Works with subject-matter experts to ensure formulas meet trusted standards like WHO, NIH, and ISO.

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