When calculating the square footage of a home, do you consider only thenet square footageor is it thegross square footage?

In other words, if the footprint is say. . . 25' by 80', that would be 2,000grosssquare feet.

If you subtract out all the wall cavities, all the cabinets, and all the closets, which total say. . . 150 square feet, then you have a total of 1,850netsquare feet.

Which square footage do you use?