Body Surface Area (BSA) Calculator
What is Body Surface Area (BSA) Calculator
The body surface area (BSA) calculator estimates the total surface area of the body from height and weight, a value widely used to dose medications such as chemotherapy. It uses the Mosteller formula, BSA = the square root of (height in cm times weight in kg divided by 3600), and also shows the Du Bois and Haycock results for comparison. The answer is given in square metres.
How to use
- Choose metric (cm, kg) or imperial (in, lbs) units.
- Enter the height.
- Enter the weight.
- Read the Mosteller BSA in m², plus the Du Bois and Haycock values.
When to use it
Dosing a drug by body surface area for a patient of 170 cm and 70 kg? Enter both and you get a Mosteller BSA of 1.82 m². The Du Bois and Haycock values sit right beside it so you can use whichever your protocol specifies.
Frequently asked questions
What is the Mosteller formula for BSA?
BSA (m²) = √(height in cm × weight in kg ÷ 3600). For 170 cm and 70 kg, that is √(11900 ÷ 3600) = √3.31 = about 1.82 m². It is the simplest and most widely used BSA formula.
Why is BSA used for drug dosing?
Many medications, chemotherapy in particular, are dosed per square metre of body surface area because it tracks metabolic rate and blood volume better than weight alone. The dose is the protocol's mg/m² multiplied by the BSA.
Why do the formulas give different values?
Mosteller, Du Bois, and Haycock were derived from different data, so they differ slightly for the same person, usually by a few percent. Use the formula your local protocol specifies and stay consistent.
Can I share this tool with my inputs pre-filled?
Yes. The URL updates automatically as you type. Copy it from the address bar or use the Share button — anyone who opens the link will see your exact inputs ready to go.
Related tools
A-a Gradient Calculator
Calculate the alveolar-arterial oxygen gradient from FiO2, PaO2 and PaCO2, and compare it to the expected value for age. Free and instant.
How Old Am I? Age Calculator
Find out exactly how old you are with this free age calculator. Enter your date of birth and get your age in years, months, days, zodiac sign, and more.
Anion Gap Calculator
Calculate the serum anion gap from sodium, chloride and bicarbonate, with optional potassium and albumin correction, to screen for metabolic acidosis.