Body Surface Area Calculator
Estimate body surface area (BSA) from height and weight using three formulas commonly referenced in clinical settings.
| Mosteller formula | 0 m² |
| Du Bois formula | 0 m² |
| Haycock formula | 0 m² |
Body Surface Area Calculator: Mosteller Formula & Complete Guide
Written by Magesh | Financial Tools & Calculation Specialist · Last updated July 31, 2026
In two sentences: A body surface area calculator estimates the total external surface of the body from height and weight, most commonly using the Mosteller formula (BSA = √(height × weight ÷ 3600)), a measurement used clinically for chemotherapy dosing and other medications where body weight alone is too imprecise. This guide breaks down the Mosteller and Du Bois formulas, worked examples, and why BSA is often considered a better dosing reference than weight alone.
What Is a Body Surface Area Calculator?
A body surface area calculator estimates the total surface area of the human body, expressed in square meters, using height and weight as inputs. Unlike BMI, which describes weight relative to height, body surface area (BSA) approximates the actual physical surface of the body — a measurement clinicians use for medication dosing, particularly chemotherapy, since BSA correlates more closely with metabolic rate and drug distribution than body weight alone.
The Body Surface Area Formulas
Mosteller formula (most widely used)
BSA (m²) = √( (Height in cm × Weight in kg) ÷ 3600 )
Du Bois and Du Bois formula (the original, 1916)
BSA (m²) = 0.007184 × Height(cm)^0.725 × Weight(kg)^0.425
Haycock formula (validated for infants, children, and adults)
BSA (m²) = 0.024265 × Height(cm)^0.3964 × Weight(kg)^0.5378
Worked Examples
Example 1: Calculating BSA with the Mosteller formula
A person is 175 cm tall and weighs 72 kg.
BSA = √( (175 × 72) ÷ 3600 )
= √(12,600 ÷ 3600)
= √3.5
≈ 1.87 m²
Example 2: A shorter walkthrough at different measurements
A person is 170 cm tall and weighs 70 kg.
BSA = √( (170 × 70) ÷ 3600 )
= √(11,900 ÷ 3600)
= √3.31
≈ 1.82 m²
Example 3: Comparing Mosteller to Du Bois for the same person
Using the 175 cm, 72 kg example from Example 1 with the Du Bois formula instead:
BSA = 0.007184 × 175^0.725 × 72^0.425
≈ 0.007184 × 42.85 × 6.09
≈ 1.87 m²
The two formulas produce nearly identical results for typical adult body sizes, which is part of why Mosteller — being far simpler to calculate — has become the default choice in most clinical settings despite Du Bois being the older, historically validated method.
Example 4: Using BSA for a clinical dosing calculation
A chemotherapy protocol prescribes a drug at 75 mg per square meter of body surface area, for a patient with a calculated BSA of 1.87 m².
Dose = 75 mg/m² × 1.87 m² ≈ 140.25 mg
This is the core reason BSA calculations matter clinically: many medications, especially chemotherapy agents, are dosed per square meter of body surface rather than per kilogram of body weight, since BSA correlates more closely with organ function and metabolic clearance than weight alone.
Step-by-Step: How to Use a Body Surface Area Calculator
- Enter height in centimeters and weight in kilograms (convert from imperial units if needed).
- Select a formula — Mosteller is the most common default for a body surface area calculator due to its simplicity and broad validation across age groups.
- Calculate BSA using the chosen formula.
- For clinical dosing purposes, multiply the body surface area calculator’s result by the prescribed dose-per-square-meter figure.
- Cross-check against a second formula (like Du Bois or Haycock) if precision matters for your specific use case, since results can vary slightly between methods.
Why BSA Matters More Than Weight Alone for Certain Calculations
Body weight alone doesn’t account for the relationship between body size and physiological processes like metabolic rate, cardiac output, and kidney function. BSA was first formulated in the early 20th century specifically to address this gap — the original Du Bois formula incorporated height alongside weight because researchers found that surface area correlated more reliably with metabolic rate than weight in isolation. This is why BSA remains the standard for chemotherapy dosing, cardiac index calculations, and normalizing kidney function measurements like glomerular filtration rate (GFR), even though it’s ultimately an estimate rather than a direct physical measurement.
Comparing BSA Formulas: Which One a Body Surface Area Calculator Should Use
- Mosteller — the simplest formula, widely adopted as the default in clinical practice due to its ease of calculation and strong validation across both adult and pediatric populations.
- Du Bois and Du Bois — the oldest, most historically established formula, though it may be less accurate for children whose body proportions differ significantly from adults.
- Haycock — specifically validated across infants, children, and adults, making it a common choice in pediatric settings.
- Gehan and George, and Boyd — alternative formulas that can produce slightly different results, occasionally used in specific research or clinical contexts.
Where a Body Surface Area Calculator Is Actually Used in Practice
A body surface area calculator isn’t just an academic exercise — it plays a direct, practical role in several areas of clinical care where getting the number right has real consequences.
Clinical contexts that rely on a body surface area calculator
- Chemotherapy dosing. As shown in the worked example above, many chemotherapy protocols are dosed per square meter of body surface rather than per kilogram, making an accurate calculation directly relevant to treatment safety and effectiveness.
- Cardiac index calculations. Cardiologists normalize cardiac output by body surface area to compare heart function fairly across patients of different sizes, since raw cardiac output alone doesn’t account for how much tissue that output needs to supply.
- Burn injury assessment. Estimating the percentage of body surface area affected by burns relies on the same underlying body surface area concept, helping guide fluid resuscitation and treatment planning.
- Kidney function normalization. Glomerular filtration rate (GFR), a key measure of kidney health, is commonly reported per 1.73 m² of body surface area, a reference figure based on average adult BSA, so an individual’s actual BSA matters when interpreting their specific results.
Frequently Asked Questions
No single formula is universally considered most accurate for every population — Mosteller is the most commonly used due to its simplicity, while Haycock is often preferred for pediatric patients since it was specifically validated across a wide age range including infants.
BSA correlates more closely with metabolic rate, cardiac output, and drug clearance than body weight alone, making it a more physiologically relevant measure for calculating a dose that will be effective without excessive toxicity.
No — BSA estimates total body surface area in square meters, primarily used for medical dosing calculations, while BMI (Body Mass Index) is a ratio of weight to height squared, used mainly as a general population-level indicator of weight category.
Yes, the formulas themselves are straightforward to calculate with accurate height and weight measurements, but clinical dosing decisions should always be made by a healthcare provider, since a self-calculated BSA is only appropriate for general reference, not medical treatment planning.
Related Calculators
- BMI Calculator
- Calorie Calculator
- Body Fat Calc
- Macro Calculator
- Water Intake Calculator
- Percentage Calc
- Weight Watcher points Calculator
- Period Calculator
- Tdee-Calculator
In summary, a body surface area calculator uses your height and weight to estimate total body surface area in square meters, and understanding why BSA is preferred over weight alone for certain medical calculations — particularly its stronger correlation with metabolic rate — explains why this measurement remains a clinical standard despite being over a century old.
About the author: Magesh is a Financial Tools & Calculation Specialist focused on building and fact-checking online calculators across health, medicine, and clinical measurement topics.
Note: This calculator and article are provided for general educational and informational purposes only and do not constitute medical advice. Body surface area calculations for medication dosing must be performed and verified by a qualified healthcare provider. Do not use this tool to determine your own or another person’s medication dosage.