Body Surface Area Calculator
Calculate body surface area for medical applications
Medical Disclaimer: This calculator is for educational purposes only. Always consult a healthcare provider for medical dosing decisions.
How to Use This Body Surface Area Calculator
- Enter your height in centimeters
- Enter your weight in kilograms
- Select your preferred formula (DuBois is most commonly used)
- Click 'Calculate BSA' to see your body surface area
- Compare results across all formulas to understand the range
Example: An adult who is 170 cm tall and weighs 70 kg has a BSA of approximately 1.82 m^2 using the DuBois formula. This value would be used by healthcare providers to calculate proper medication dosages for drugs like chemotherapy agents.
Tip: The DuBois formula is used most commonly in clinical practice. Mosteller is simpler to calculate manually. Haycock is often preferred for pediatric patients.
Why Use a Body Surface Area Calculator?
Body surface area (BSA) is used in medicine to calculate drug dosages, estimate kidney function, and assess burn injuries - situations where body size significantly affects treatment.
- Healthcare providers calculating chemotherapy drug dosages
- Determining proper dosing for medications that require BSA-based calculations
- Estimating glomerular filtration rate (GFR) normalized to body size
- Calculating cardiac index in cardiology assessments
- Assessing burn injury extent (percentage of body surface affected)
- Research studies requiring standardized body size measurements
Understanding Your Results
Average adult BSA ranges from 1.5 to 2.0 m^2. Values outside this range may require adjusted medical dosing.
| Result | Meaning | Action |
|---|---|---|
| < 1.5 m^2 | Below Average BSA | Common in smaller adults, children, or elderly. Drug doses may need reduction. |
| 1.5 - 2.0 m^2 | Average Adult BSA | Standard range for most adults. Typical dosing calculations apply. |
| > 2.0 m^2 | Above Average BSA | Common in larger adults. May require increased doses for some medications. |
Meaning: Below Average BSA
Action: Common in smaller adults, children, or elderly. Drug doses may need reduction.
Meaning: Average Adult BSA
Action: Standard range for most adults. Typical dosing calculations apply.
Meaning: Above Average BSA
Action: Common in larger adults. May require increased doses for some medications.
Note: BSA-based dosing is most critical for medications with narrow therapeutic windows, like chemotherapy drugs. Always follow healthcare provider guidance.
About Body Surface Area Calculator
Formula
DuBois: BSA = 0.007184 x Height^0.725 x Weight^0.425 Height in cm, weight in kg, result in m^2. Mosteller: sqrt(Height x Weight / 3600). Haycock (pediatric): 0.024265 x Height^0.3964 x Weight^0.5378.
Current Standards: Average adult BSA is approximately 1.7 m^2 for women and 1.9 m^2 for men. Chemotherapy and certain cardiac medications use BSA to personalize dosing. Standard dosing assumes approximately 1.73 m^2.
Frequently Asked Questions
Why is BSA used instead of weight for some drug dosing?
Many physiological processes like drug clearance by the kidneys and liver scale better with body surface area than with weight alone. A tall, thin person and a short, heavy person of the same weight have different metabolic rates and drug distribution. BSA better captures this variation. It's especially important for toxic drugs like chemotherapy where overdosing causes serious harm and underdosing reduces effectiveness.
Which BSA formula is most accurate?
No single formula is universally most accurate. DuBois is the standard in most clinical settings and is validated across adult populations. Mosteller gives nearly identical results with simpler math. Haycock is often preferred for children. For obese patients, some clinicians use ideal body weight or adjusted body weight rather than actual weight in BSA calculations. The differences between formulas are usually small (5-10%).
How is BSA used in burn assessment?
The 'Rule of Nines' estimates burn extent as a percentage of BSA: head and neck = 9%, each arm = 9%, chest = 18%, back = 18%, each leg = 18%, groin = 1%. Knowing total BSA and burn percentage helps calculate fluid resuscitation requirements using formulas like Parkland. For example, a 50% BSA burn on someone with 2 m^2 BSA affects 1 m^2 of skin.
Does BSA change significantly with weight fluctuations?
BSA changes with weight, but less dramatically than you might expect due to the exponential relationship. A 10% weight change typically results in about a 3-4% BSA change. For most medication dosing, BSA is recalculated periodically (monthly for chemotherapy patients, for example) to account for weight changes during treatment.
Can I use this calculator for my child?
The calculator works for all ages, but the Haycock formula is often preferred for pediatric patients as it was developed specifically for children. DuBois and Mosteller were developed using adult data and may be less accurate for very young children. For infants and children, always verify BSA calculations with healthcare providers who can use age-appropriate formulas and reference ranges.