you have to measure the entire square footage of each room, do not add the ceiling in with the walls as you have to use 5/8" drywall and walls use 1/2", next determine what size you want to use ie: 4*8, 4*12 and so on, now cut your sqft by the size of the sheet and multiply that by 1.2 to account for waste. or use a contractors calculator app as it dose this for you including tape and mud its what i do and the formula for the same thing w/out using it is a long formula
23- 4×12 sheets would be cutting it close. Always grab a couple extra sheets to save a trip back to home depot. In case of mistakes or accidents.
Walls and ceiling.
