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Body Surface Area Calculator

Calculate Body Surface Area (BSA) using the Mosteller formula - the standard method used in clinical settings for medication dosing, burn assessment, and cardiac index calculations.

Your Measurements

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Body Surface Area (m²)
For clinical or medication dosing decisions, always confirm this figure with a healthcare provider.

Mosteller Formula

Mosteller Formula

BSA (m²) = √((Height in cm × Weight in kg) ÷ 3600)

Worked Example

Height: 175 cm, Weight: 70 kg

BSA = √((175 × 70) ÷ 3600)
BSA = √(12,250 ÷ 3600)
BSA = √3.403 ≈ 1.84 m²

Other Common BSA Formulas (for reference)

Du Bois: BSA = 0.007184 × Height(cm)^0.725 × Weight(kg)^0.425
Haycock: BSA = 0.024265 × Height(cm)^0.3964 × Weight(kg)^0.5378

These typically produce results within 2-3% of the Mosteller formula.

Common Profiles

Average adult: 70kg, 175cm
BSA ≈ 1.84 m²
Smaller adult: 60kg, 160cm
BSA ≈ 1.63 m²
Child: 20kg, 110cm
BSA ≈ 0.78 m²
Larger adult: 95kg, 188cm
BSA ≈ 2.23 m²

Frequently Asked Questions

BSA is primarily used in clinical medicine to calculate accurate drug dosages, especially for chemotherapy and other medications with a narrow safety margin, since dosing by body surface area is often more precise than dosing by weight alone. It is also used to assess burn severity, cardiac index, and kidney function (GFR normalization).
This calculator uses the Mosteller formula, BSA = √((height in cm × weight in kg) ÷ 3600), which is widely used in clinical practice for its simplicity and accuracy. Other formulas like Du Bois or Haycock exist and produce very similar results within a small margin of each other.
BSA accounts for both height and weight together, which correlates more closely with metabolic rate, blood volume, and organ function than weight alone. Two people with the same weight but very different heights can have meaningfully different BSA values, which matters for medications where dosing precision affects both efficacy and toxicity risk.
The average adult BSA is approximately 1.7 square meters (m²), though this varies with height and weight - ranging from roughly 1.3 m² for a smaller adult to over 2.2 m² for a larger adult. Infants and children have proportionally smaller BSA, typically under 1.0 m².
No. This calculator provides the BSA value for informational and educational purposes only. Medication dosing based on BSA should always be calculated and verified by a qualified healthcare provider or pharmacist, since incorrect dosing - especially for chemotherapy or other high-risk drugs - can have serious health consequences.

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Body Surface Area Calculator - A Key Number in Clinical Medicine

Body Surface Area (BSA) is an estimate of the total surface area of a person's body, expressed in square meters. Unlike everyday health metrics like BMI, BSA is used almost exclusively in clinical settings - most importantly for calculating precise medication dosages, since BSA correlates more closely with metabolic rate and organ function than body weight alone.

Quick reference (Mosteller formula): BSA (m²) = √((Height in cm × Weight in kg) ÷ 3600)

Why BSA Matters More Than Weight for Certain Medications

For most everyday medications, dosing by weight alone works well enough. But for drugs with a narrow therapeutic window - meaning the difference between an effective dose and a toxic dose is small, as is common with chemotherapy agents - BSA-based dosing provides a more precise estimate of how a person's body will process the drug. This is because BSA reflects both height and weight together, correlating more closely with blood volume, cardiac output, and kidney filtration rate than weight does on its own.

The Mosteller Formula vs. Other BSA Formulas

Several formulas exist for estimating BSA, including Du Bois (the oldest, from 1916), Haycock, and Mosteller. This calculator uses the Mosteller formula because of its simplicity and because it has been validated as accurate across a wide range of body sizes, including in pediatric populations. The different formulas typically agree within 2-3% of each other for most adult body types, so the choice of formula rarely changes the clinical decision being made.

Other Clinical Uses of BSA

  • Chemotherapy dosing: Many cancer treatment protocols specify drug doses in milligrams per square meter of BSA rather than milligrams per kilogram of body weight.
  • Cardiac index: Cardiac output is often normalized by BSA to produce the cardiac index, allowing fair comparison of heart function across patients of different body sizes.
  • Burn assessment: The percentage of BSA affected by burns is a key factor doctors use to determine treatment urgency and fluid resuscitation needs.
  • Kidney function (GFR): Glomerular filtration rate is frequently normalized to a standard BSA of 1.73 m² to allow comparison across patients of different sizes.

An Important Caution

This calculator is intended for informational and educational purposes. Any medication dosage that depends on BSA - particularly high-risk medications like chemotherapy - should always be calculated, double-checked, and prescribed by a qualified healthcare provider or pharmacist using validated clinical tools, not a general-purpose online calculator.

How this calculator works, and where the numbers come from

The Body Surface Area applies the standard formula for this calculation to the values you enter and updates the result as you type. The calculation itself happens in your browser, and the page explains the method so you can check any result by hand.

Please note: This tool gives general estimates based on published population formulas. It is not medical advice and does not replace assessment by a doctor, dietitian or other qualified professional.

Sources and further reading

Learn more

Read our guide: What BMI Tells You, and What It Quietly Misses

Last reviewed: by the CalcQube Editorial Team. See our editorial policy for how we build and check calculators, or report an error.