Hi Pu, Use the "Measure Volume and Area" dialog under menu Tools / Volume Data to show the volume in cubic Angstroms enclosed by your map contour surface. It will update automatically as the threshold changes. Make sure the voxel size of your map is set correctly in Angstroms because the reported enclosed volume uses that. That is set in the Volume Viewer dialog under the Coordinates panel. To estimate molecular weight from the volume you could use an approximate value for globular proteins from the literature of 1.21 cubic Angstroms per Dalton (Harpaz 1994). http://www.cgl.ucsf.edu/chimera/tutorials/eman07/chimera-eman-2007.html#part... Tom

Hi Tom,

I have a question to ask you.

I'm working on a 3D EM map from single particle reconstuction using Chimera. I would like to know the total volumn of this 3D model or its molecular weight when I change thresholds. How can I do it or where can I find this value?

Best regards

Pu Qian