Why is body surface area used instead of body weight?

Many physiological measures — such as metabolic rate, cardiac output, and certain drug clearances — scale more closely with surface area than with raw weight. Dosing by BSA can therefore reduce over- or under-treatment in patients of unusual size.

What is an average adult BSA?

A commonly cited average for adults is about 1.7 m², with most adults falling roughly between 1.5 and 2.2 m² depending on height and weight. Children have substantially smaller values.

How does the Du Bois formula compare to Mosteller?

Both are widely used and usually agree within a couple of percent. This calculator uses the Du Bois and Du Bois equation; the Mosteller formula is a simpler square-root alternative that some clinicians prefer for quick mental math.

Can I use BSA for chemotherapy dosing myself?

No. BSA-based dosing involves clinical judgement, capping rules, and patient-specific factors. Use this figure for general understanding only and let your care team determine any actual dose.

Body Surface Area Calculator

Height

Weight

lbs

Body Surface Area2.00 m²

Body surface area (BSA) is the total external area of the body, expressed in square metres, and is widely used in medicine to scale drug doses, cardiac output, and fluid needs more fairly than weight alone. This calculator uses the classic Du Bois and Du Bois formula, which combines your height and weight into a single area estimate. It is intended for general reference; clinical dosing should always be confirmed by a healthcare professional.

Formula

BSA (m²) = 0.007184 × weight(kg)^0.425 × height(cm)^0.725

weight: Body weight in kilograms (pounds × 0.453592)
height: Height in centimetres (inches × 2.54)
BSA: Body surface area in square metres

How it works

Enter your height in inches and weight in pounds; the tool converts them to centimetres and kilograms (× 2.54 and × 0.453592).
It applies the Du Bois formula, which raises weight and height to fixed exponents and multiplies by a constant.
The result is your body surface area in square metres, rounded to two decimal places.

Worked example

An adult 5 ft 10 in (70 in) tall weighing 180 lb computes their BSA.

Convert: height 70 × 2.54 = 177.8 cm; weight 180 × 0.453592 = 81.65 kg.
BSA = 0.007184 × 81.65^0.425 × 177.8^0.725.
= 0.007184 × 6.341 × 43.82 ≈ 1.996 m².

BSA ≈ 2.00 m².

Frequently asked questions

Why is body surface area used instead of body weight?: Many physiological measures — such as metabolic rate, cardiac output, and certain drug clearances — scale more closely with surface area than with raw weight. Dosing by BSA can therefore reduce over- or under-treatment in patients of unusual size.
What is an average adult BSA?: A commonly cited average for adults is about 1.7 m², with most adults falling roughly between 1.5 and 2.2 m² depending on height and weight. Children have substantially smaller values.
How does the Du Bois formula compare to Mosteller?: Both are widely used and usually agree within a couple of percent. This calculator uses the Du Bois and Du Bois equation; the Mosteller formula is a simpler square-root alternative that some clinicians prefer for quick mental math.
Can I use BSA for chemotherapy dosing myself?: No. BSA-based dosing involves clinical judgement, capping rules, and patient-specific factors. Use this figure for general understanding only and let your care team determine any actual dose.

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