What fits in 25 square feet.

A medium moving box is roughly 18 x 18 x 16 inches, about 3 cubic feet. Stacked to head height across the whole floor you could physically fit well over 40, but you would not be able to reach any of them. Five to eight alongside a piece of furniture is the realistic figure; 15 to 25 is achievable only with nothing else in the unit and no need to get at the bottom layer.

A queen is 60 by 80 inches, so 5 ft by 6 ft 8 in. Stood on its long edge it is 6 ft 8 in tall against an 8 ft ceiling and exactly the 5 ft width of the unit. It goes in, but it takes a whole wall and leaves you working around it. A 5x10 is the sensible size if a queen is in the load.

A twin is 38 by 75 inches and a full 54 by 75. Both stand upright against a wall comfortably and leave usable floor in front, unlike the queen.

A dining chair occupies about 1.5 sqft of floor and a nightstand about 2 sqft. Three or four such pieces take under half the floor and can be stacked seat-to-seat.

A large suitcase is roughly 31 x 21 x 12 inches, about 4.5 cubic feet, and nests inside a smaller one. A floor lamp stands in a corner at under 1 sqft. Neither is ever the binding constraint.

This is what the size is actually for. A 27-gallon tote is about 3.6 cubic feet; twenty of them is 72 cubic feet, roughly a third of the unit, stacked four high on half the floor.

A 50 inch TV is about 44 in wide, so it stands against the 5 ft wall in its box. A mini fridge is around 20 x 20 x 33 in. The three together take roughly a quarter of the floor. Worth putting somewhere climate controlled.

A banker box is 15 x 12 x 10 inches, about 1 cubic foot. Fifteen of them stacked five high is three columns on a 3 ft by 1 ft footprint, so the constraint is the aisle you need, not the volume.

A road motorcycle is 7 ft to 7 ft 6 in long. The diagonal of a 5 ft by 5 ft floor is 7 ft 1 in and the door sits on one of those walls, so there is no angle that works. This is the clearest reason to step up to a 5x10, which has 10 ft of depth.