Body Surface Area Calculator

Body surface area, or BSA, is the total area of the outside of the body measured in square metres.

Clinicians use it to scale things that track surface area better than body weight does, most notably chemotherapy doses, cardiac index, and some measures of kidney function and burn extent.

This calculator takes a height and weight and estimates BSA using four well-established formulas so you can see how they compare on the same person.

The Mosteller formula is the simplest and most widely used in practice: it is the square root of height times weight divided by 3600.

The classic Du Bois & Du Bois equation from 1916 is the historical reference, while the Haycock and Gehan-George formulas were derived to fit children and a broader population.

Because each was fitted to different data, they can disagree by a few percent, so the tool shows all four results alongside the one you select.

You can enter measurements in metric (centimetres and kilograms) or imperial (inches and pounds), and the conversion happens automatically.

Every calculation runs locally in your browser — nothing is uploaded, logged or stored — so it is private and works offline.

This tool is for education and quick estimates and is not a substitute for professional medical judgement; clinical dosing should always be confirmed by a qualified provider.