Calculation of surface volumes

You want to know the volume for certain surface ond/or area in Autodesk® AutoCAD® Civil 3D®. 
If a grading is involved in the surface creation you have the possibility to use the Grading Volume Tools from the Grading Creation Tools. 
You also can create a Volume Surface and read the volumes from the Statistics Tab in the surface propoerties. 
With adding a surface legend table it is also possible to add volume data to the table. But this data is different compared to the two other methods.

Causes:

There is a difference between the volume numbers of a volume surface table and a volume analysis.

Solution:

• Volume Analysis:
  • Always two surfaces are involved
  • The grading and volume surface methods calculate cut and fill values.
  • It's the volume difference between two surfaces or - in other words, the volumes needed to fill the vertical gaps between two surfaces
• The legend volume is the de facto volume available:
  • It is calculated for one surface only
  • It most often differs from the volume analysis even though you create the table on the volume surface

Example 1: 
 
 

Example 2: