Accurately determine your Body Surface Area (BSA) based on your height and weight.
BSA Calculator
Enter height in centimeters (cm).
Enter weight in kilograms (kg).
Your BSA Results
—
Height: — cm
Weight: — kg
BSA Formula: Du Bois Formula
The Du Bois formula is commonly used to estimate Body Surface Area (BSA).
BSA vs. Weight for Constant Height
Chart showing how BSA changes with weight for a fixed height (175 cm).
BSA Calculation Table (Du Bois Formula)
Height (cm)
Weight (kg)
BSA (m²)
160
55
—
170
65
—
180
75
—
Sample BSA calculations using the Du Bois formula for different height and weight combinations.
What is BSA Calculations Height and Weight?
BSA calculations height and weight refer to the process of determining an individual's Body Surface Area (BSA) using their physical measurements of height and weight. BSA is a significant physiological metric that represents the total surface of the human body. It is widely used in medical fields, particularly in pharmacology and oncology, for calculating drug dosages, chemotherapy regimens, and assessing various physiological parameters. Unlike Body Mass Index (BMI), which is a simple ratio, BSA is a more accurate indicator of metabolic mass and is considered a better predictor for certain medical calculations. Understanding your BSA can be crucial for personalized medical treatments and research.
Who should use it?
Healthcare professionals, researchers, and individuals undergoing specific medical treatments (like chemotherapy) are the primary users of BSA calculations. Patients undergoing treatments where dosage is critical often need to know their BSA. It's also used in some physiological studies and clinical trials.
Common misconceptions:
A common misconception is that BSA is the same as BMI. While both use height and weight, they serve different purposes and are calculated differently. BMI is a general indicator of body fat, whereas BSA is more directly related to metabolic rate and drug absorption. Another misconception is that BSA is only relevant for adults; it is also calculated for children, though specific pediatric formulas or adjustments might be used.
BSA Calculation Formula and Mathematical Explanation
The most widely accepted and commonly used formula for calculating Body Surface Area (BSA) is the Du Bois formula. This formula was developed by Du Bois and Du Bois in 1916 and remains a standard in clinical practice.
The Du Bois Formula
The formula is expressed as:
BSA = 0.007184 × Height0.725 × Weight0.425
Where:
BSA is the Body Surface Area.
Height is measured in centimeters (cm).
Weight is measured in kilograms (kg).
Step-by-step derivation:
1. Measure the individual's height in centimeters (cm).
2. Measure the individual's weight in kilograms (kg).
3. Raise the height measurement to the power of 0.725.
4. Raise the weight measurement to the power of 0.425.
5. Multiply the results from steps 3 and 4.
6. Multiply the product by the constant 0.007184.
7. The final result is the BSA in square meters (m²).
Variables Table:
Variable
Meaning
Unit
Typical Range
Height (H)
Individual's height
Centimeters (cm)
Adults: 140 – 200 cm
Weight (W)
Individual's weight
Kilograms (kg)
Adults: 40 – 120 kg
BSA
Body Surface Area
Square Meters (m²)
Adults: 1.4 – 2.2 m²
Exponent for Height
Power to which height is raised
Unitless
0.725
Exponent for Weight
Power to which weight is raised
Unitless
0.425
Constant
Empirical constant in the Du Bois formula
Unitless
0.007184
It's important to note that while the Du Bois formula is standard, other formulas like Mosteller, Gehan and George, and Boyd exist, each with slightly different constants and exponents, potentially yielding marginally different BSA values. However, the Du Bois formula is the most frequently cited and used in clinical settings.
Practical Examples (Real-World Use Cases)
Understanding BSA is crucial for accurate medical dosing. Here are a couple of practical examples:
Example 1: Chemotherapy Dosing
A patient, Mr. John Smith, is scheduled for a chemotherapy treatment. His doctor needs to calculate the correct dosage of a specific drug based on his BSA.
Inputs:
Height: 180 cm
Weight: 75 kg
Calculation using the Du Bois formula:
BSA = 0.007184 × (180)0.725 × (75)0.425
BSA = 0.007184 × 48.56 × 11.78
BSA ≈ 1.93 m²
Output: Mr. Smith's BSA is approximately 1.93 m².
Interpretation: If the prescribed chemotherapy dose is 500 mg/m², the total dose for Mr. Smith would be 500 mg/m² × 1.93 m² = 965 mg. This ensures he receives an appropriate and safe amount of medication tailored to his body size.
Example 2: Pediatric Medication Dosage
A child, Sarah, weighs 20 kg and is 120 cm tall. She needs a specific antibiotic, and the dosage is calculated based on BSA.
Inputs:
Height: 120 cm
Weight: 20 kg
Calculation using the Du Bois formula:
BSA = 0.007184 × (120)0.725 × (20)0.425
BSA = 0.007184 × 30.87 × 6.59
BSA ≈ 1.46 m²
Output: Sarah's BSA is approximately 1.46 m².
Interpretation: If the antibiotic dosage is 150 mg/m², Sarah's total dose would be 150 mg/m² × 1.46 m² = 219 mg. This precise calculation is vital for pediatric care to ensure efficacy and avoid toxicity.
How to Use This BSA Calculator
Our BSA calculator is designed for simplicity and accuracy, making it easy for anyone to determine their Body Surface Area. Follow these steps:
Enter Height: In the "Height" field, input your height in centimeters (cm). For example, if you are 5 feet 9 inches tall, you would convert this to centimeters (approximately 175 cm) and enter that value.
Enter Weight: In the "Weight" field, input your weight in kilograms (kg). For instance, if you weigh 150 pounds, convert this to kilograms (approximately 68 kg) and enter it.
Calculate: Click the "Calculate BSA" button. The calculator will instantly process your inputs using the Du Bois formula.
View Results: Your calculated BSA will be displayed prominently in square meters (m²). You will also see your input height and weight, and confirmation of the formula used.
Reset: If you need to perform a new calculation or correct an entry, click the "Reset" button to clear the fields and results.
Copy Results: Use the "Copy Results" button to easily copy your main result, intermediate values, and key assumptions to your clipboard for use elsewhere.
How to read results: The primary result is your BSA in square meters (m²). This value is crucial for medical professionals determining drug dosages or other treatments. The intermediate values confirm the inputs used and the formula applied.
Decision-making guidance: While this calculator provides the BSA value, it is essential to consult with a healthcare professional for any medical decisions. Your BSA is one factor among many used in clinical practice.
Key Factors That Affect BSA Results
While the BSA calculation itself is straightforward using height and weight, several underlying factors influence these measurements and, consequently, the resulting BSA. Understanding these can provide context:
Age: As individuals grow, their height and weight change significantly, directly impacting BSA. Pediatric BSA calculations are particularly important due to rapid growth and development. Adult BSA tends to stabilize but can change with age-related weight fluctuations.
Sex: On average, males tend to have a higher BSA than females of the same height and weight due to differences in body composition (muscle mass vs. fat mass). While the Du Bois formula doesn't explicitly differentiate by sex, population averages show these trends.
Body Composition: The ratio of muscle mass to fat mass can influence weight. Individuals with higher muscle mass might have a different metabolic rate and potentially a different BSA interpretation, although the formula itself only uses total weight.
Genetics: Inherited traits can influence an individual's natural height and frame size, which are the primary determinants of BSA.
Nutritional Status: Malnutrition or obesity can significantly alter weight, thereby affecting BSA calculations. Consistent monitoring of weight is crucial for accurate BSA determination, especially in clinical settings.
Hydration Levels: While less impactful on long-term BSA calculations, significant changes in body water content can temporarily affect weight measurements, leading to slight variations in calculated BSA if measured at that specific time.
Measurement Accuracy: The precision of height and weight measurements is paramount. Inaccurate readings due to faulty equipment or improper technique will lead to an incorrect BSA value. Standardized measurement protocols are essential in clinical research and practice.
Frequently Asked Questions (FAQ)
Q1: What is the standard unit for BSA?
A: The standard unit for Body Surface Area (BSA) is square meters (m²).
Q2: Is the Du Bois formula the only way to calculate BSA?
A: No, other formulas like Mosteller, Gehan and George, and Boyd exist. However, the Du Bois formula is the most commonly used and widely accepted in clinical practice.
Q3: Can I use BMI instead of BSA for drug dosages?
A: No, BMI is not a substitute for BSA in medical dosing. BSA is considered a more accurate measure of metabolic mass for drug calculations, especially for chemotherapy.
Q4: Does BSA change throughout life?
A: Yes, BSA changes significantly during childhood and adolescence as height and weight change. In adulthood, it tends to be more stable but can fluctuate with significant weight changes.
Q5: How accurate is the BSA calculation?
A: The accuracy depends on the precision of the height and weight measurements and the chosen formula. The Du Bois formula is an estimation, but it's considered reliable for clinical purposes.
Q6: Why is BSA important for chemotherapy?
A: Chemotherapy drugs are often toxic, and their dosage needs to be carefully calibrated to the patient's body size to maximize effectiveness while minimizing severe side effects. BSA provides a standardized way to achieve this.
Q7: Can I use feet/inches and pounds with this calculator?
A: This calculator requires height in centimeters (cm) and weight in kilograms (kg). You will need to convert your measurements before entering them.
Q8: What is a typical BSA range for an adult?
A: For adults, the typical BSA range is generally between 1.4 m² and 2.2 m². However, this can vary based on individual height and weight.
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var weightInput = document.getElementById('weight');
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var weightError = document.getElementById('weightError');
var resultsSection = document.getElementById('resultsSection');
var mainResult = document.getElementById('mainResult');
var intermediate1 = document.getElementById('intermediate1');
var intermediate2 = document.getElementById('intermediate2');
var intermediate3 = document.getElementById('intermediate3');
var bsaChartCanvas = document.getElementById('bsaChart').getContext('2d');
var tableRow1BSA = document.getElementById('tableRow1BSA');
var tableRow2BSA = document.getElementById('tableRow2BSA');
var tableRow3BSA = document.getElementById('tableRow3BSA');
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errorElement.style.display = 'block';
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errorElement.textContent = ";
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function calculateBSA() {
var heightCm = heightInput.value;
var weightKg = weightInput.value;
var isHeightValid = validateInput(heightCm, heightError, 'Height');
var isWeightValid = validateInput(weightKg, weightError, 'Weight');
if (!isHeightValid || !isWeightValid) {
resultsSection.style.display = 'none';
return;
}
var h = parseFloat(heightCm);
var w = parseFloat(weightKg);
var bsa = 0.007184 * Math.pow(h, 0.725) * Math.pow(w, 0.425);
bsa = bsa.toFixed(3); // Round to 3 decimal places
mainResult.textContent = bsa + ' m²';
intermediate1.textContent = 'Height: ' + h + ' cm';
intermediate2.textContent = 'Weight: ' + w + ' kg';
intermediate3.textContent = 'BSA Formula: Du Bois Formula';
resultsSection.style.display = 'block';
updateChart(h);
updateTable();
}
function resetCalculator() {
heightInput.value = '175';
weightInput.value = '70';
heightError.textContent = ";
heightError.style.display = 'none';
weightError.textContent = ";
weightError.style.display = 'none';
resultsSection.style.display = 'none';
mainResult.textContent = '–';
intermediate1.textContent = 'Height: — cm';
intermediate2.textContent = 'Weight: — kg';
intermediate3.textContent = 'BSA Formula: Du Bois Formula';
updateChart(175); // Reset chart to default height
updateTable();
}
function copyResults() {
var resultsText = "BSA Calculation Results:\n";
resultsText += "————————\n";
resultsText += "Main Result: " + mainResult.textContent + "\n";
resultsText += intermediate1.textContent + "\n";
resultsText += intermediate2.textContent + "\n";
resultsText += intermediate3.textContent + "\n";
resultsText += "Formula Used: Du Bois Formula (BSA = 0.007184 × Height^0.725 × Weight^0.425)\n";
resultsText += "Assumptions: Height in cm, Weight in kg.\n";
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textArea.value = resultsText;
document.body.appendChild(textArea);
textArea.select();
try {
var successful = document.execCommand('copy');
var msg = successful ? 'Results copied!' : 'Failed to copy results.';
console.log(msg);
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tempMsg.textContent = msg;
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function calculateBSAPure(h, w) {
if (h <= 0 || w <= 0) return 0;
return (0.007184 * Math.pow(h, 0.725) * Math.pow(w, 0.425)).toFixed(3);
}
function updateTable() {
var bsa1 = calculateBSAPure(160, 55);
var bsa2 = calculateBSAPure(170, 65);
var bsa3 = calculateBSAPure(180, 75);
tableRow1BSA.textContent = bsa1 + ' m²';
tableRow2BSA.textContent = bsa2 + ' m²';
tableRow3BSA.textContent = bsa3 + ' m²';
}
function updateChart(fixedHeight) {
var weights = [40, 50, 60, 70, 80, 90, 100];
var bsaValues = [];
var bsaValuesFor160 = []; // Add a second series for comparison
for (var i = 0; i 0) {
updateChart(h);
} else if (!isHeightValid) {
resultsSection.style.display = 'none';
}
});
weightInput.addEventListener('input', function() {
var h = parseFloat(heightInput.value);
var w = parseFloat(this.value);
var isWeightValid = validateInput(this.value, weightError, 'Weight');
if (isWeightValid && !isNaN(h) && h > 0) {
updateChart(h);
} else if (!isWeightValid) {
resultsSection.style.display = 'none';
}
});
// Basic Chart.js integration (assuming Chart.js is available globally)
// If Chart.js is not globally available, you'd need to include it via CDN or local file.
// For this example, we assume it's available.
// Example CDN:
// If Chart.js is not included, the chart will not render.
// For a self-contained HTML file, you would typically embed Chart.js or use SVG.
// Since the prompt requires pure HTML/JS, and Chart.js is a library,
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// However, Canvas is a native element, and Chart.js is a common way to use it.
// If Chart.js is disallowed, a pure SVG chart would be an alternative.
// Placeholder for Chart.js inclusion if needed:
//