ChimeraX docs icon

Tool: Measure Volume and Area

Measure Volume and Area reports the total surface area (sum of triangle areas) and enclosed volume of a surface model. All types of surface models are handled, including volume data isosurfaces. To measure individual disconnected blobs within a single surface model, see Measure and Color Blobs . To measure the solvent-accessible surface area of an atomic structure, the command measure sasa should be used instead. See also: Volume Viewer, measure area, measure volume, surface splitbycolor, measurements

Measure Volume and Area can be started from the Volume Data section of the Tools menu. The tool window can be moved, resized, etc.

The Surface of interest should be chosen from the list of available surfaces. The surface area and enclosed volume are reported in the dialog in the physical units of the data, typically Å3 for volume and Å2 for area.

Surfaces are composed of triangles. Anything that changes the positions of the vertices in a surface will change its area and enclosed volume, for example:

Update automatically (on by default) indicates volume and area should be recomputed automatically whenever such a change occurs. Otherwise, a new calculation can be triggered by clicking Update.

Clicking Help shows this page in the Help Viewer.


Clipping and zoning are ignored. The calculation uses the full surface, even if part of it is hidden by clipping or zoning (e.g., with surface zone or volume zone).

Surface holes. The volume enclosed by a surface with holes is calculated by assuming each hole has a planar cap. These caps are not displayed or included in the surface area determination. The number of holes is reported, as planar caps may not represent missing data very well. Holes in a volume data isosurface may occur at the boundary of the data, but by default these will already be covered with planar caps. Such boundary caps will be included in the surface area calculation and will not be reported as holes.

UCSF Resource for Biocomputing, Visualization, and Informatics / May 2021