Enter your weight and height in metric (kg/cm) or imperial (lb/in), then choose from four standard formulas. The calculator instantly computes your body surface area in square meters and displays the result with the formula name used.
Body Surface Area
Free BSA calculator – no sign‑up
Calculate Your Body Surface Area in Seconds
Determine your BSA using multiple validated formulas: Du Bois, Mosteller, Haycock, and more. Essential for medication dosing, cardiac index, and clinical assessments — all free, private, and instant.
Know Your Body Surface Area for Accurate Medical Calculations
Body Surface Area (BSA) is a key measurement used in healthcare for dosing chemotherapy, calculating cardiac output, and determining renal function. Our BSA Calculator uses your height and weight, applying several validated formulas — Du Bois, Mosteller, Haycock, Gehan & George, and Boyd — to give you an accurate estimate. You’ll see the results side by side, along with a visual comparison and an explanation of how BSA is used in clinical practice. It’s fast, free, and your health data stays completely private.
What Is a Body Surface Area Calculator?
A Body Surface Area calculator is a free online tool that estimates the total surface area of your body in square meters (m²). You simply provide your height and weight, and the calculator uses established mathematical formulas (such as Du Bois, Mosteller, and Haycock) to compute your BSA. Different formulas may yield slightly different results, so our tool displays several commonly used equations side by side. BSA is crucial in many medical contexts — it’s used to calculate cardiac index, adjust chemotherapy doses, and estimate glomerular filtration rate (GFR). It is also employed in burn assessments and physiological studies. The calculator is designed for quick, private use and is not a substitute for professional medical evaluation.
How to Use the BSA Calculator
Enter Your Height & Weight
Provide your measurements in either imperial (feet/inches, pounds) or metric (centimeters, kilograms). The calculator accepts both unit systems.
Instantly View Your BSA
The tool automatically computes your body surface area using all five common formulas and highlights the Mosteller value as a simple reference.
Understand the Results
Compare the outputs and learn how BSA applies to medication dosing, renal function, and more — no sign‑up required.
How the BSA Calculator Computes Your Surface Area
Each formula uses a slightly different equation based on weight (in kilograms) and height (in centimeters). The **Mosteller** formula is the simplest: BSA = √((Height × Weight) ÷ 3600). **Du Bois** is the most widely cited: BSA = 0.007184 × Height^0.725 × Weight^0.425. **Haycock**, **Gehan & George**, and **Boyd** use similar power functions. The calculator performs all calculations locally on your device and displays the results in square meters to two decimal places.
Key BSA Formulas
Mosteller: √(H × W / 3600)
Du Bois: 0.007184 × H^0.725 × W^0.425
H = height in cm, W = weight in kg. All formulas give BSA in m².
Key Features of This BSA Calculator
Five Validated Formulas
See results from Du Bois, Mosteller, Haycock, Gehan & George, and Boyd in one clean table.
Visual Formula Comparison
A bar chart instantly shows how the different equations agree (or vary) for your specific measurements.
Dual Unit Support
Enter height in feet/inches or centimeters, weight in pounds or kilograms — the calculator handles the conversions.
Private & Secure
Your health measurements never leave your device. Nothing is ever uploaded or shared.
Benefits of Knowing Your Body Surface Area
- ✅ Precise medication dosing – many chemotherapy and pediatric drugs are dosed per m²
- ✅ Better health metrics – cardiac index and creatinine clearance are normalized to BSA
- ✅ Burn assessment – the “rule of nines” uses BSA to estimate total burn area
- ✅ Fitness & physiology – heat loss, metabolic rate, and fluid requirements are related to surface area
- ✅ Standardized comparison – BSA provides a common denominator for comparing physiological parameters
Common BSA Formulas at a Glance
Mosteller (1987)
Simplest formula: √((height × weight) ÷ 3600). Widely used due to ease of calculation. Highly accurate for adults and children.
Du Bois & Du Bois (1916)
The classic standard: 0.007184 × H^0.725 × W^0.425. Still the most cited formula in medical literature.
Haycock (1978)
Validated in infants and children: 0.024265 × H^0.3964 × W^0.5378. Often used in pediatric dosing.
Gehan & George (1970) / Boyd (1935)
Additional formulas that provide alternative estimates. The calculator shows all so you can compare.
How BSA Is Used in Clinical Medicine
BSA is most frequently used to calculate the cardiac index (cardiac output ÷ BSA) and to dose chemotherapeutic agents. It also provides a more accurate normalization than weight alone for renal function (e.g., GFR is often corrected to 1.73 m²). Additionally, burn units rely on BSA to estimate the percentage of body affected and fluid resuscitation needs. Knowing your BSA can help you understand your medical reports and have informed discussions with healthcare providers.
The Mosteller Formula: Why It’s So Popular
Simple Math
You only need to multiply height and weight, divide by 3600, and take the square root. It requires no exponents or logarithms.
Excellent Accuracy
Studies show it correlates extremely well with the more complex Du Bois formula (r > 0.99) across a wide range of body sizes.
Example BSA Calculation
A person is 170 cm tall and weighs 70 kg. Using Mosteller: BSA = √((170 × 70) ÷ 3600) = √(11900 ÷ 3600) = √3.3056 ≈ 1.82 m². Du Bois: 0.007184 × 170^0.725 × 70^0.425 ≈ 1.81 m². Haycock: 0.024265 × 170^0.3964 × 70^0.5378 ≈ 1.82 m². The values are nearly identical. The calculator presents all these results alongside a chart, so you can see the tight agreement between formulas.
How to Use BSA in Your Health Records
Many electronic health records automatically compute BSA from your height and weight. If you want to double‑check the number or need it for a personal calculation (e.g., understanding a medication dose), this calculator provides a quick, independent verification. Keep a note of your BSA, especially if you’re undergoing treatment where dosing is size‑dependent.
Factors That Influence Body Surface Area
- 📏 Height
- ⚖️ Weight
- 🧬 Body composition (fat vs. muscle)
- 📅 Age (BSA changes during growth)
- 🚻 Gender (indirectly through average size)
- 🤰 Pregnancy (temporarily increases BSA)
- 📋 Amputations (reduce BSA)
- 🏥 Obesity (formulas may vary slightly)
Detailed Pediatric BSA Scenario
Scenario: Child, height 110 cm, weight 18 kg. Calculate BSA for medication dosing.
- ✅ Mosteller: √((110 × 18) ÷ 3600) = √(0.55) ≈ 0.74 m²
- ✅ Haycock: 0.024265 × 110^0.3964 × 18^0.5378 ≈ 0.73 m²
- ✅ Du Bois: 0.007184 × 110^0.725 × 18^0.425 ≈ 0.72 m²
- ✅ The pediatric oncologist would use the BSA to calculate the precise chemotherapy dose per square meter.
Who Can Use This BSA Calculator?
- 🩺 Patients undergoing chemotherapy – understand how your dose is determined
- 👶 Parents of children on medication – many pediatric drugs are weight‑ or BSA‑based
- 📋 Medical students & residents – quickly compute BSA for clinical calculations
- 💊 Pharmacists – verify dosing for BSA‑adjusted prescriptions
- 🎓 Anyone curious about their body metrics – learn another way your body is measured
Key BSA Terms
- Body Surface Area (BSA)
- The total surface area of the human body, expressed in square meters (m²).
- Mosteller Formula
- A simple, accurate BSA formula: √((H × W) ÷ 3600), where H is in cm and W is in kg.
- Du Bois Formula
- The classic BSA equation: 0.007184 × H^0.725 × W^0.425, still widely referenced.
- Haycock Formula
- Often used for children: 0.024265 × H^0.3964 × W^0.5378.
Tips for Accurate BSA Measurements
- Use your current height and weight — don’t rely on old measurements.
- If you are overweight or underweight, be aware that BSA formulas are most accurate for people of average body composition.
- For medical decisions, always use the formula specified by your doctor or pharmacist.
- Recalculate periodically during growth or significant weight change.
- Remember that BSA is an estimate; clinical judgment is essential.
Advantages of This BSA Calculator
- ✅ 100% free – no sign‑up, no ads
- ✅ Five formulas displayed simultaneously
- ✅ Supports both metric and imperial units
- ✅ Visual chart comparing formula results
- ✅ Works on any device
- ✅ Private – your health data never leaves your device
Limitations of BSA Calculators
BSA formulas provide an estimate; actual body surface area varies with body composition. In extreme obesity or severe cachexia, the formulas may be less accurate. This calculator is for educational purposes and should not replace professional clinical measurement when precise dosing is critical.
Accuracy of Results
The Mosteller formula is validated in adults and children and matches Du Bois within 1–2%. All formulas use the same input data, so results typically agree within a few hundredths of a square meter.
Security and Privacy
All calculations are performed locally in your browser. No height, weight, or personal information is ever transmitted, stored, or shared. You can use the tool offline after the page loads.
Mobile‑Friendly Design
The BSA calculator is fully responsive. Use it on your smartphone, tablet, or desktop — all inputs, charts, and results adapt seamlessly to any screen size.
Frequently Asked Questions
What is a normal body surface area?
The average adult BSA is about 1.6–1.9 m² for women and 1.8–2.1 m² for men, but it varies widely with height and weight. There is no single “normal” — it’s an individual metric.
Which BSA formula should I use?
Mosteller is the simplest and most commonly used in clinical practice today. Du Bois is the classic reference. For children, Haycock is often recommended. The calculator shows all, allowing you to compare.
Can BSA be used to calculate drug doses?
Yes, many chemotherapy agents and pediatric medications are dosed per square meter of BSA. Always follow your doctor’s prescription — never self‑dose.
How often does BSA change?
BSA changes whenever your height or weight changes significantly. It should be recalculated before each cycle of chemotherapy or whenever a BSA‑based dose is administered.
Is BSA the same as BMI?
No. BMI is a measure of body fat based on height and weight. BSA is the total external surface area. Both are derived from height and weight but serve different purposes.
Is my personal data safe?
Absolutely. All calculations are local. No information is ever sent to a server or stored.
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Conclusion: Small Measurement, Big Clinical Impact
Body Surface Area is a deceptively simple number with profound medical importance. This calculator gives you instant access to a key piece of your health profile, with multiple formulas for confidence. Enter your measurements now and add this valuable metric to your health knowledge.
Ready to Calculate Your BSA?
Enter your height and weight now – free, private, and instant.