Neagtive volume of a mesh

I imported a CADMATIC 3d model in to the Rhino to get volume of the model.
In Rhino model the CADMATIC 3d model converted to the meshes.
The reason of getting volume is that I need to confirm the CADMATIC weight with Rhino outcome.
After confirming the correctness of the meshes then I want to get the total surface area.
But I can not make confirmed the weight because Rhino gives the negative value for the volume.
(-1.08 cubic millimeters).
I want to get correct volume of the meshes.
(There are meshes having no naked faces but having negative values for volume)

Hi Sani -

Which file format did you use to get your model into Rhino? Which file formats does CADMATIC support?

Can you post the file?

Normals pointing into the volume instead of out of the volume will result in Volume command returning a negative number. Dir can be used to check the normal directions of meshes. Dir with the Flip option or Flip command will flip the normals.