computrtutr

OK, so I'm making a custom sub box out of fiberglass. I need to get within .8 cubic feet and 1.5. Here is my initial thought: Create a backside fiberglass structure to conform to the space in my trunk on the left side (I have a 2000 A4, so it's where the toolbox/CD changer go). I'll be taking out part of that wall so I can conform the box to the inside and not lose too much trunk space. How do I measure the volume of the enclosure? This will be for a 12" sub. My plan is to take the fiberglass piece that fits the interior, fortify it, and measure the volume using water. I used a converter to get an idea- apparently it will take 95 8-oz cups to equal .8 cubic feet. Does this sound right to anyone, or is there a better way to figure volume? I will be subtracting out the volume of the sub.