I didn't actually do the math so I don't know what mistake (if any, aside from writing the wrong units) occurred. I just thought it was kind of funny. Didn't mean to make a big deal of it either; I just knew his volume SHOULDN'T be larger than my master bedroom.
OP, sounds like you've gotten yourself on the right track with online calculators. Any other issues, feel free to ask. I'll try not to make fun of simple errors.