I have bleachcalc (wonderful thing, that!) and it has a volume calc.
16' x 32' IG VINYL 3' to 8'. I emphasized the "VINYL" part because the walls don't go nearly straight down in the deep end. You could easily say the avg. depth is 5.5 ft given the dimensions, but that doesn't count the sloped sides in the deep end. W/o sloped sides, it's 21k+ gal. One pool guy said it's closer to 17k. The the walls are only flat about 3'-4' down in the deep end, then they slope inwards at about a 45degree angle.
Any clues or tools to calculate this?