About Flooring Calculations
Flooring starts with square footage, but the material decides the waste. Tile and plank get ordered by the box, and each box covers a set area, so you round up to whole boxes every time. That builds in some overage, but you still add a waste factor: 10% for a straight lay and 15% for a diagonal or herringbone pattern where the cuts pile up.
Carpet is its own animal because it comes in 12-foot rolls. A 13-foot-wide room either needs a seam or wastes a full foot of width down its length, so how the installer plans the cuts changes how much you buy. That's why carpet square footage often runs well above the room's actual floor area.
Epoxy and resin go by coverage rate per gallon at a given thickness, and that thickness varies a lot between a thin garage coat and a self-leveling pour. Read the product's spread rate before you order. And don't forget the layer underneath: underlayment, thinset, and adhesive get figured separately and are easy to forget until you're standing at the counter.
Run these numbers first to dodge dye-lot pain. Buy all your tile or carpet in one lot so the color matches, with enough waste built in that you don't have to chase a second order in a different shade. Keep a box back for future repairs.