Drywall calculator
Enter the room; the material list follows. Openings deducted.
Sheets, joint compound, tape and screws for one room, with the door and window openings already deducted and the finish level setting the mud.
Worked example: a 12 × 12 ft room, 8 ft ceilings
One door and two windows, hung in 4 × 8 sheets at 16 in framing, finished to Level 4, the standard for flat paint under ordinary light.
Where the count actually comes from
The sheet count is area ÷ 32, rounded up, plus a waste allowance. The waste allowance is not padding: a room with a door and two windows has three openings to cut around, and every cut leaves an offcut that rarely fits anywhere else. Ten percent is the usual figure; 15% is realistic for an irregular ceiling or a room with a lot of corners.
A seam that does not sit on a stud or joist will crack, usually within the first heating season, and no amount of mud hides it.
Why the finish level changes the mud order
Joint compound is the largest variable in the job, and it is set by how smooth the finish has to be, not by the size of the room. A garage at Level 2 takes roughly half the compound of a living room at Level 4, and a Level 5 skim coat over the whole surface takes nearly twice as much again. The finish levels page explains which one applies where: getting this wrong is either wasted money or a wall that looks lumpy under a lamp.