there are a few methods...
1.) boolean to get the internal volume
2.) revolve an open profile
in either case, you will want to take advantage of multibody support ...
There are some ways to get internal volume, I like to use Delete regions command.
Here is a video about steps:
I hope this helps.
Thanks for the link.
The only issue I had was when I had to BOUND the edge as it was profiled.
Because I wanted to know the volume for and oil quantity I cut the box down to the max level and then I was able to BOUND the edge.
Worked a treat.