The calculations which are provided by most sites is a simplified 1/2 the volume of "box". There are a few that try to include a fudge factor for the hopper designs by multiplying by .85. Anyway back some 15 or so years ago when I had the pool built I had sat down and calculated a volume and somehow concluded 23000 gal. Having come up short on my shocking quantities I was thinking I was off. So this morning I attempted this again. After much thought and trying to visualize the geometric shapes at the intersecting hopper sides I have come up with 22100 gal based on including steps and estimated equipment volume. I saw a similar post under Chemistry 101 which vendor info for a 18X36 was just over 19000 gal. Has anyone ever drawn this out and performed a similar calculation? By the way I found that my deep end was only 7'8" versus 8'. Anybody else's like that?