Drywall Calculator
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Result
Sheets to buy
- Board area
- 586.3 sq ft including waste
- Joint compound
- 6 gallons of joint compound
- Joint tape
- 235 ft of tape
- Screws
- 6 lb of screws
- Wall area
- 416 sq ft (52 ft perimeter × 8 ft)
- Ceiling area
- 168 sq ft
- Openings deducted
- 51 sq ft for 1 door(s) and 2 window(s)
- The ceiling adds 168 sq ft — 29% of the total board area. It is also the hardest part to hang, and the reason a drywall lift is worth renting for anything beyond a small room.
- Sheet size changes the joint length more than the sheet count. At 4 × 8 ft this room needs 19 sheets; at 4 × 12 it would need 13. Fewer, longer sheets mean fewer butt joints to tape, and taping is where the labour and the visible defects are.
Sheets by size
The same board area in each available sheet size. Fewer sheets means fewer joints to finish.
| Sheet size | Coverage | Sheets needed |
|---|---|---|
| 4 × 8 ft (yours) | 32 sq ft | 19 |
| 4 × 9 ft | 36 sq ft | 17 |
| 4 × 10 ft | 40 sq ft | 15 |
| 4 × 12 ft | 48 sq ft | 13 |
How many sheets of drywall do I need?
Divide the total wall and ceiling area by the coverage of one sheet — 32 square feet for a 4 by 8. A 14 by 12 ft room with an 8 ft ceiling has 533 square feet after deducting openings, needing 19 sheets with waste.
area = perimeter × height + (length × width) sheets = ⌈area × (1 + waste) ÷ sheet coverage⌉- perimeter
- 2 × (length + width) — the distance around the room
- length × width
- The ceiling, if you are boarding it
- sheet coverage
- 32 sq ft for 4 × 8, 48 for 4 × 12
Wall area comes from the perimeter rather than from adding four walls separately, which is both quicker and less error-prone. The ceiling is the part most estimates miss, and it is not a rounding error — on a 14 by 12 foot room with an 8 foot ceiling the ceiling is 168 square feet against 416 of wall, nearly 30% of the job. Openings are deducted at 21 square feet for a standard door and 15 for a typical window, though on a wall with many openings the offcuts are rarely reusable, so deducting them and then adding waste back is the honest approach. The sheet size decision is the interesting one, because it changes the labour more than the material. Longer sheets create fewer butt joints, and butt joints are both the slowest thing to tape and the most likely to show once the wall is painted. A 4 by 12 sheet covers half again what a 4 by 8 does, so it cuts the joint count substantially — at the cost of weight that makes it hard to handle alone, especially overhead. Compound, tape and screws all scale with board area rather than sheet count, at roughly a gallon, 40 feet and a pound per hundred square feet.
- Add length and width, then double it for the perimeter.
- Multiply the perimeter by the ceiling height for wall area.
- Add length times width if you are boarding the ceiling.
- Deduct 21 sq ft per door and 15 per window.
- Add ten percent for cutting, then divide by the sheet coverage.
Worked example: A 14 × 12 ft room with an 8 ft ceiling, one door, two windows, boarding the ceiling
A 14 × 12 ft room with an 8 ft ceiling, one door, two windows, boarding the ceiling
The perimeter is 2 × (14 + 12) = 52 ft, so the walls are 52 × 8 = 416 square feet. The ceiling adds 14 × 12 = 168, giving 584 square feet gross — and that ceiling is 29% of the total, which is why forgetting it is such a costly omission. Deducting 21 square feet for the door and 15 each for the two windows removes 51, leaving 533 square feet of board. Adding 10% for cutting around the openings and corners brings it to 586.3. At 32 square feet per 4 × 8 sheet that is 18.3 sheets, so you buy 19. Choosing 4 × 12 sheets instead needs only 13, and more importantly cuts the number of butt joints to tape by a third. The consumables follow the area rather than the sheet count: 6 gallons of joint compound, 235 feet of tape and 6 pounds of screws.
What each drywall input means
- Room length
- Interior length of the room.
- Room width
- Interior width of the room.
- Ceiling height
- Floor to ceiling. An 8 ft ceiling lets sheets run horizontally with no cutting, which is why it is the standard.
- Include the ceiling
- The ceiling is usually boarded too, and it is the part people forget. On a 14 × 12 room it adds nearly 30% to the area.
- Sheet size
- Longer sheets create fewer joints to tape and finish, which is where the labour is — but they are heavier and harder to handle alone.
- Doors
- Each deducts 21 sq ft, a standard 3 × 7 ft opening.
- Windows
- Each deducts 15 sq ft, a typical 3 × 5 ft opening.
- Waste allowance
- Covers cutting around openings, corners and damaged sheets.
What this drywall does not account for
- The ceiling is usually boarded and is often forgotten. On a typical room it is close to 30% of the total area, and it is the hardest part to hang without a lift.
- Deducting openings and then adding waste back is the honest approach, because offcuts from around a window are rarely large enough to reuse.
- Sheet size changes the labour more than the material. Longer sheets mean fewer butt joints, which are the slowest to tape and the most likely to show after painting.
- Ceilings between 8 and 9 feet leave a filler strip when standard sheets are hung horizontally. A 4 × 9 sheet or 54-inch board avoids an extra joint on every wall.
- Moisture-resistant board is required in bathrooms and behind tile, and fire-rated Type X is required on garage ceilings and shared walls. Both cost more and are heavier.
- Compound, tape and screws scale with board area, not sheet count — roughly a gallon, 40 feet and a pound per hundred square feet for a three-coat finish.
- Corner bead, furring, adhesive and primer are separate purchases not counted here. Primer is not optional on new board, which absorbs paint unevenly.
Frequently asked questions
How many sheets of drywall for a 12x14 room?
Nineteen 4 × 8 sheets, including the ceiling and a 10% waste allowance. The room has 584 square feet gross, 533 after deducting a door and two windows, and 586 once waste is added.
How much does one sheet of drywall cover?
A 4 × 8 sheet covers 32 square feet, a 4 × 10 covers 40 and a 4 × 12 covers 48. Larger sheets mean fewer joints to tape, which is where most of the labour sits.
Should I use 4x8 or 4x12 drywall?
Use the longest sheet you can handle. A 4 × 12 cuts the butt-joint count by about a third on a typical wall, and butt joints are both slow to finish and prone to showing.
How much joint compound do I need?
About one gallon per 100 square feet of board for a three-coat finish. A room with 586 square feet of drywall needs roughly 6 gallons, plus tape at around 40 feet per 100 square feet.
Do I need to subtract windows and doors?
Yes, at roughly 21 square feet per door and 15 per window — but keep the waste allowance, since offcuts from around openings are rarely big enough to use elsewhere.
How many screws per sheet of drywall?
Around 32 to 36 screws for a 4 × 8 sheet on 16-inch framing. By weight it works out to roughly one pound of screws per 100 square feet of board.
Sources and review
Last reviewed .