How to calculate how many drywall sheets you need
Drywall is sold by the sheet but used by the area, so the job is to find the area you cover and divide it by the area of one sheet. Georgia-Pacific's ToughRock Wallworks Guide lays out the method: the walls of a room are its length plus width, times 2, times the height; the ceiling is length times width. Measure the doors and windows and subtract them to get the net area. Then divide by the sheet size and allow 10 to 15 percent extra for cutting and piecing.
Example: a 12 by 14 ft bedroom with 8 ft walls has 2 × (12 + 14) × 8 = 416 square feet of wall. A 3 by 7 ft door and two 3 by 5 ft windows take off 51, which leaves 365 square feet. With 10 percent for waste that is 401.5 square feet, and a 4 by 8 ft sheet covers 32, so you need 13 sheets for the walls. The 168 square foot ceiling takes 6 more, 19 sheets in all. The calculator rounds walls and ceilings up on their own, because ceilings often get a different board.
In this calculator you enter every wall as a line with its length and height. For a plain rectangular room that is two lines with "2" in the count. Rooms with an alcove, a sloped wall or a stair wall work the same way: break them into rectangles. A gable end is a triangle; enter it as a rectangle of half its height to get the same area.
Drywall sheets for common room sizes
The table assumes 8 ft walls, one 3 by 7 ft door, two 3 by 5 ft windows and 10 percent for waste. Each sheet column shows the walls plus the ceiling.
| Room | Net walls, sq ft | Ceiling, sq ft | 4 × 8 ft sheets | 4 × 12 ft sheets |
|---|---|---|---|---|
| 10 × 10 ft | 269 | 100 | 10 + 4 | 7 + 3 |
| 10 × 12 ft | 301 | 120 | 11 + 5 | 7 + 3 |
| 12 × 12 ft | 333 | 144 | 12 + 5 | 8 + 4 |
| 12 × 14 ft | 365 | 168 | 13 + 6 | 9 + 4 |
| 14 × 16 ft | 429 | 224 | 15 + 8 | 10 + 6 |
| 16 × 20 ft | 525 | 320 | 19 + 11 | 13 + 8 |
Screws, tape and joint compound
Once you know the board area, the rest of the material follows from it. The calculator uses figures that two manufacturers publish and works them out from the net area, before waste:
- Screws: Georgia-Pacific's estimating chart lists about 1,250 screws per 1,000 square feet of 1/2 or 5/8 inch wallboard, against about 2,000 nails. USG's Sheetrock panel FAQ spaces screws 12 inches apart on ceilings and 16 inches on walls, and nails 7 inches on ceilings and 8 inches on walls, so ceilings need more fasteners than walls. Check how many screws come in the box you buy.
- Joint tape: the same Georgia-Pacific chart lists one 250 ft roll for 500 square feet and two rolls for 800 square feet. The calculator counts 500 ft of tape per 1,000 square feet and rounds up to 250 ft rolls.
- Joint compound: USG's FAQ says about two 4.5 gallon pails of its ready-mixed all-purpose compound finish 1,000 square feet of wallboard, and that the coverage is comparable to its other ready-mixed compounds. That is about 9 gallons, or 34 liters, per 1,000 square feet.
These are the manufacturers' averages, not exact counts. The coverage printed on your pail and the walls you actually have decide the real amount, so buy a little extra rather than run out halfway through a coat.
Which sheet size to choose
USG lists its standard Sheetrock panels at 48 inches wide and 6 to 16 ft long, so 4 by 8, 4 by 10 and 4 by 12 ft are all one width with different lengths. Longer sheets mean fewer seams to tape. Georgia-Pacific suggests installing the board across the joists and studs, avoiding end joints where possible, perhaps by buying 12 ft board instead of 8 ft depending on the room size, and staggering the end joints you cannot avoid.
Longer sheets are also heavier and harder to carry up a staircase or around a corner, so 4 by 8 ft is the easier choice when you work alone. For metric boards, pick one of the metric sizes or choose Other size and enter the width and length of the board your store sells. The square footage calculator helps with odd room shapes, and the paint calculator takes over once the walls are finished.
How to use the drywall calculator
- 1Choose feet or meters. Enter each wall with its length and height, and how many walls of that size the room has.
- 2Add the ceiling with its length and width if you cover it too, and add every door and window with its width and height.
- 3Pick the sheet size and a waste allowance. Enter a price per sheet if you want the cost.
- 4Read the sheets to buy for walls and ceiling, plus the screws, tape and joint compound, then copy the list or the link.
Frequently asked questions
How many sheets of drywall do I need for a 12 x 12 room?
A 12 by 12 ft room with 8 ft walls has 384 square feet of wall and a 144 square foot ceiling. Take off a 3 by 7 ft door and two 3 by 5 ft windows and 333 square feet of wall are left. With 10 percent for waste, that is 12 sheets of 4 by 8 ft for the walls and 5 for the ceiling, 17 in all.
How many screws are in a sheet of drywall?
Georgia-Pacific estimates about 1,250 screws per 1,000 square feet of 1/2 or 5/8 inch wallboard, which is about 40 for a 4 by 8 ft sheet. USG spaces screws 12 inches apart on ceilings and 16 inches on walls, so a ceiling sheet takes a few more than a wall sheet.
How much joint compound do I need?
USG expects about two 4.5 gallon pails of its ready-mixed all-purpose compound to finish 1,000 square feet of wallboard, about 9 gallons. That is roughly 0.3 gallons per 4 by 8 ft sheet. Other products cover differently, so check the coverage on the pail you buy.
How much drywall tape do I need?
The estimating chart in Georgia-Pacific's ToughRock guide lists one 250 ft roll of tape for 500 square feet of wallboard and two rolls for 800 square feet. The calculator uses one 250 ft roll per 500 square feet, which is 500 ft of tape per 1,000 square feet.
Should I subtract doors and windows?
Georgia-Pacific's guide says to measure the doors and windows, subtract them to get the net area, and then add 10 to 15 percent for cutting and piecing. The calculator does the same. Leave small cutouts such as outlets and switch boxes in the area.
How much extra drywall should I buy for waste?
Georgia-Pacific recommends 10 to 15 percent over the net area for cutting and piecing, so the calculator starts at 10 percent. Choose 15 percent for rooms with many corners, angled ceilings or lots of openings, where more of each sheet ends up as offcuts.