Body Surface Area Calculator

Body surface area (BSA) is an estimate of the total external area of your body, expressed in square metres. Unlike weight or BMI, it isn't a measure of health or body composition — it's a measure of body size, and it turns out to be a more useful basis than weight for a number of medical calculations.

The reason clinicians reach for BSA is that many physiological quantities scale with surface area rather than mass. Medication and especially chemotherapy doses are frequently calculated per square metre, and measures such as cardiac index and some kidney-function estimates are normalised to BSA so that people of different sizes can be compared fairly.

Typical adult BSA is roughly 1.5–2.0 m². Because it simply reflects your dimensions, there's no "good" or "bad" value — a taller or larger person naturally has a higher BSA. Treat the number as descriptive, and leave any dosing or clinical use to a qualified professional using your full clinical picture.

Formula. We use the Mosteller equation: BSA (m²) = √( height(cm) × weight(kg) ÷ 3600 ). Enter your height and weight in metric or imperial units — the calculator converts to centimetres and kilograms first, so the result is identical either way.

Why Mosteller. Published in the New England Journal of Medicine in 1987, the Mosteller formula is the most widely used simplified BSA calculation in clinical practice because it's easy to compute and agrees closely with older, more complex equations such as Du Bois & Du Bois (1916).

Confidence. We label BSA high confidence: the formula is a clinical standard. That reflects the method's standing, not a claim of exactness — real body surface area varies between individuals, and BSA describes your size rather than diagnosing anything.