RoomCalc
Drywall tools

Drywall calculator

Enter the room; the material list follows. Openings deducted.

Room dimensions

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.

Gross wall area (48 ft perimeter × 8 ft)384 sq ft
Less openings (1 door, 2 windows)−51 sq ft
Ceiling144 sq ft
Total to cover477 sq ft
4 × 8 sheets with 10% waste17 sheets
Joint compound at Level 42 × 4.5 gal buckets
Paper tape2 roll (572 linear ft of joint)
Drywall screws at 16 in centres572 screws (1.9 lb)
Paint: 2 coats plus primer3 gal finish + 2 gal primer

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.

17 sheets, staggered so no seam lines up with the next courseSheet edges land on framing: joints between sheets are where cracks start

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.

Frequently asked questions

How much drywall do I need?
Measure the wall area (room perimeter × ceiling height), take off about 21 sq ft per door and 15 sq ft per window, add the ceiling if you are boarding it, then divide by 32 for 4 × 8 sheets and add 10% for offcuts. A 12 × 12 ft room with 8 ft ceilings, one door and two windows comes to 12 sheets for the walls alone and 17 with the ceiling.
How many sheets of drywall for a 12×12 room?
17 sheets of 4 × 8, covering 477 sq ft of walls and ceiling with openings deducted and 10% waste. Rooms with more corners or openings need more.
How much joint compound do I need?
About 7.2 gallons for a room this size at Level 4, which is 2 standard 4.5 gallon bucket. Level 5 roughly doubles it.
How many screws per sheet of drywall?
About 32 screws per 4 × 8 sheet at 16 in framing, or 40 at 12 in framing. Space them every 12 in on a ceiling and every 16 in on walls, closer along the edges.
How much drywall tape do I need?
About 38 linear feet of joint per 4 × 8 sheet once the butt joints, corners and ceiling angle are counted, so a standard 500 ft roll of paper tape finishes roughly 13 sheets. Buy one roll more than the count: a roll that runs out halfway down a joint costs more time than the roll.
How much does a sheet of drywall weigh?
A standard 1/2 in 4 × 8 sheet weighs roughly 50 to 57 lb, and a lightweight 1/2 in sheet about 38 to 42 lb. 5/8 in fire-rated board is around 70 lb, and a 12 ft sheet is half as heavy again as an 8 ft one, which is the practical reason most ceilings are hung with a panel lift.
Should I deduct doors and windows from the drywall area?
Yes, the calculator does it for you, using 21 sq ft for a standard door and 15 sq ft for a standard window. You still board around them, so the deduction is only for what you do not cover.

Related tools

Paint calculator

Gallons of finish and primer for the same room.

Drywall finish levels

Levels 1 to 5, and where each one applies.

Which drywall mud to use

The compound for each coat, and how much per sheet.

Whole-house estimator

Several rooms rolled into one shopping list.

Drywall for a garage

Drywall sheets, mud and screws for one, two and three car garages, walls and ceiling, plus