If the ratio of my cat's weight to litter box size = 1.65 sq.ft/8 lbs.
Then a litter box built for me would = x sq.ft/150 lbs.
With that said, if I were to buy a litter box for myself based on the ratio of pounds to square feet, my litter box would need to be 31 sq.ft.
My cubicle is 20 square feet.
My cubicle is not big enough to sh*t in!