What is a normal body surface area?

An average adult is around 1.7 m2. Values commonly range from about 1.5 to 2.1 m2 depending on height and weight.

Which BSA formula should I use?

Mosteller is the most common in practice because it is simple to verify by hand. Du Bois remains widely cited in the literature.

Why is body surface area used instead of weight?

Physiological quantities such as cardiac output and metabolic rate track surface area more closely than body weight, so indexing to BSA makes comparisons between people fairer.

Is BSA used for chemotherapy dosing?

Many protocols do dose by BSA. The specific formula and rounding rules are set by the protocol, so clinical use should follow that guidance rather than a general calculator.

Body Surface Area Calculator

Calculate body surface area with the Mosteller, Du Bois, Haycock and Gehan-George formulas.

Enter your details and your result will appear here.

What Is Body Surface Area?

Body surface area (BSA) is the total external surface of the body in square metres. It is used in clinical settings to scale measurements such as cardiac index and some drug doses, and it is calculated from height and weight.

Understanding Your Body Surface Area Result

BSA scales more closely with metabolic rate and blood volume than body weight does, which is why it is preferred for indexing physiological measurements. Several formulas exist because each was fitted to a different sample; for adults of typical size they agree closely, and they diverge more at the extremes of height and weight. An average adult BSA is roughly 1.7 m2.

How Is Body Surface Area Calculated?

Mosteller: BSA (m2) = sqrt(height (cm) x weight (kg) / 3600)

Methodology

Mosteller (1987) is used as the default: the square root of height in centimetres multiplied by weight in kilograms, divided by 3600. Du Bois and Du Bois (1916), Haycock (1978) and Gehan and George (1970) are shown alongside, each a power function of height and weight.

Worked Example

For someone 5 ft 9 in (175 cm) and 70 kg, the Mosteller formula gives the square root of (175 x 70 / 3600), which is 1.84 m2. Du Bois returns 1.85 m2 and Haycock 1.85 m2, so the three agree to within a rounding step.

Important Limitations

BSA formulas were derived from small samples, several of them nearly a century ago, and they are less reliable at the extremes of body size, including severe obesity, where different formulas can differ by more than 10%. This calculator is for general information; clinical dosing decisions should use the formula and units specified by the relevant protocol.

Frequently Asked Questions

What is a normal body surface area?: An average adult is around 1.7 m2. Values commonly range from about 1.5 to 2.1 m2 depending on height and weight.
Which BSA formula should I use?: Mosteller is the most common in practice because it is simple to verify by hand. Du Bois remains widely cited in the literature.
Why is body surface area used instead of weight?: Physiological quantities such as cardiac output and metabolic rate track surface area more closely than body weight, so indexing to BSA makes comparisons between people fairer.
Is BSA used for chemotherapy dosing?: Many protocols do dose by BSA. The specific formula and rounding rules are set by the protocol, so clinical use should follow that guidance rather than a general calculator.