"Ever built ikea furniture? Let’s say it’s a bookshelf. The bookshelf when built will be 1’ x 2.5’ x 5’ tall. You only need 2.5’2 of floorspace with 5’ vertical clearance for the bookshelf.
However, when you unbox it, lay out the parts on the floor and get to building, you need far more floor space than the bookshelf will occupy.
5’2 (x2) for the sidewalls, and the base is 2.5’2, each shelf will also be 2.5’2, space for the tools and fasteners and instructions, and also space for you to move around while assembling it, and space to move the parts around while you’re assembling, etc.”
a good analogy for just about anything you want to get done.