I really can’t fathom why every person who has replied so far has decided to complicate the matter so much. Finding the volume of an object is way simpler than all of the suggestions supplied.
You simply select the whole object you want to find the volume for and if not already made into a group or component then do so. Once you have created a group simply right click and select entity info.
The volume is the 4th drop down info box in the default tray on your right as illustrated in the attached jpeg
even in this example which has a square mortice the volume is calculated, though I did find it questionable. I did this to calculate the volume of concrete I would need per post as a client of mine requires 5 2400mmx100mmx100mm posts erected for a lean to car port.
I know that for a 2400mmx100mmx100mm post I will need approximately 2 foot in the ground for maximum support and stability with a distance of 100mm all around on every side of each square post, therefore giving a depth of 600mmx300mmx300mm. Personally I was intriguied by sketchup’s answer for the volume and found it questionable? to sate my curiosity I deconstructed the form into 9 equal cubes/rectangles as I know the mortice is 100mmx100mm and the distance from the outside of the mortice to the edge of the block is 100mm each side(giving a total distance of 300mm for each side of the full block) this left me 8 cubes of equal size in the end because I obviously don’t count the mortice as this represents my 100mmx100mm post and I don’t need the volume for this(basic physics - no 2 entities of matter or no 2 masses can occupy the same space at any given time - duh!) in the end I calculated the volume of one of these cubes (0.01 m³) and multiplied it by 8 which gave me an end total of 0.08m³ I then multiplied this again by the number of holes I required for my posts. I know this is a very elaborate and elongated answer but hopefully it may help someone who is struggling with calculating volumes for materials. total concrete needed for my project in the end was - 0.4 m³ or
400 cm³ respectively due to there being 5 posts 0.08 m³ x 5.