Drywall maths, one room at a time.

Because "how much drywall do I need" means four different jobs. A garage is one big wall with one enormous hole in it. A basement is mostly a ceiling problem. A bathroom is 200 sq ft and eleven edges. A page that covers all three does none of them properly, so each room gets its own defaults, its own waste allowance and its own list of what the number cannot see.

Run each room on its own page and add the sheet counts. Do not add the areas and divide once — every room has its own waste, and a single big division rounds down in a way that bites you at the counter. Save each room as you go and your browser keeps the list.

It is a purchasing number, not a cut list. Area plus a waste allowance divided by the sheet size, rounded up — the same method the trade uses to order board. It will not lay out your seams, and it cannot see the box you have to build around a duct. The waste allowance is the dial that covers the difference, which is why every page tells you when to turn it up.