What Is Body Surface Area?

Body surface area is the odd one out in this library. It is not a health score, it has no good or bad values, and most people encounter it only in a clinical context — which is exactly what it was built for.

The Mosteller formula

BSA(m²) = √( height(cm) × weight(kg) / 3600 )

Published by Mosteller in the New England Journal of Medicine in 1987, this is the most widely used simplified BSA equation in clinical practice. Its appeal is that it is accurate enough for the job and simple enough to compute by hand.

For someone 170 cm tall weighing 68 kg:

√(170 × 68 / 3600) = √(11560 / 3600) = √3.2111 = 1.79 m²

Our Body Surface Area Calculator handles imperial input by converting first.

What it's used for

BSA is primarily a dosing quantity. Certain medications — chemotherapy agents most notably — are dosed per square metre of body surface area rather than per kilogram of body weight, because BSA correlates better than weight alone with some physiological parameters relevant to drug handling.

It also appears in some cardiac and renal calculations, where measurements are normalised to body size for comparison.

What it is not used for is assessing whether someone is healthy. There is no "good" BSA.

No risk bands, deliberately

Every other calculator in the Fitness & Body category returns something you can interpret as better or worse. BSA does not, and we do not attach bands to it.

Typical adult BSA falls roughly in the 1.5–2.0 m² range. That is a descriptive observation about the population, not a target — being at 1.7 or 1.9 says nothing about your health. It is a physiological quantity like your height, not a score like your BMI.

Accuracy

We label BSA high confidence, reflecting that Mosteller is a standard, clinically used estimation. It is still an estimate — real body surface area varies between people of identical height and weight, and no formula measures it directly.

The older Du Bois and Du Bois equation from 1916 is a documented alternative and remains in use; it gives slightly different figures. As with ideal weight formulas and 1RM formulas, the existence of several accepted equations is a reminder that each is an approximation of something not directly measured.

If you're checking a medical dose

A caution worth stating plainly: if you are calculating BSA to check a medication dose, treat this calculator as a reference and not as a verification of clinical care. Dosing decisions account for factors beyond BSA, different institutions may use different formulas, and your clinical team has information this tool does not.

If a dose seems wrong to you, raise it with your pharmacist or doctor rather than resolving it with a website.

The bottom line

BSA estimates your body's surface area from height and weight, mainly for clinical dosing. Typical adult values run roughly 1.5–2.0 m², and there is no healthy or unhealthy value — which is why this calculator shows no bands. Calculate yours on the Body Surface Area Calculator.