Paint, drywall, tile, and trim — coverage and counts for a room at a time.
Every coverage figure on a paint can or a tile box assumes a surface that rarely exists: flat, sealed, and uniform. Real walls are porous, textured, or a colour you are trying to bury, and each of those costs coverage the label does not deduct. These calculators start from the room you actually have. Openings come out of the wall area rather than being ignored. Second coats are counted as a second coat. Tile returns a box count at your chosen layout, with the cut waste a diagonal or offset pattern really produces, and flooring, carpet, trim, and wallpaper each follow the unit their supplier sells in.