The short answer
Add the wall area to the ceiling area, subtract doors and windows, add 10% for waste and divide by 32 sq ft for a 4 × 8 sheet. A 12 × 14 ft room with 8 ft walls needs 13 sheets for the walls alone and 19 sheets with the ceiling. With 4 × 12 sheets the same room takes 9 or 13.
Step 1: Measure the surfaces
Measure the length, width and ceiling height. Walls are the perimeter times the height, and the ceiling is length times width. Include closets and small utility spaces if you are finishing them as well.
Wall area = 2 × (length + width) × height
Ceiling area = length × width
Step 2: Subtract doors and windows
Our calculator takes 20 sq ft off for each door and 15 sq ft for each window. Large openings such as sliding doors or archways deserve their own measurement. Small cutouts for outlets and switches do not count, since the offcuts are part of your waste.
Step 3: Choose the sheet size
Family Handyman gives the standard coverage: a 4 × 8 ft sheet covers 32 sq ft and a 4 × 12 ft sheet covers 48 sq ft. It also notes that 12 ft sheets mean fewer seams and less waste, but a 4 × 8 sheet weighs about 55 lbs and a 12 footer about 82 lbs, and they must fit through your stairwell.
Seams matter because every joint has to be taped and finished. The best way to avoid butt joints, according to Family Handyman, is to use sheets long enough to span the whole wall or ceiling.
| Sheet | Area | Weight | Best for |
|---|---|---|---|
| 4 × 8 ft | 32 sq ft | about 55 lbs | Most rooms, one person can carry it |
| 4 × 10 ft | 40 sq ft | in between | Longer walls and ceilings |
| 4 × 12 ft | 48 sq ft | about 82 lbs | Long walls, fewer seams, needs help |
Step 4: Add waste
Use 10% for a simple rectangular room. Raise it to 15% for rooms with many openings, angles or short cuts. The drywall calculator has both as presets.
Sheets = (wall area + ceiling area − openings) × (1 + waste %) ÷ area of one sheet, rounded up
Worked example: a 12 × 14 ft room with 8 ft walls
- Walls: 2 × (12 + 14) × 8 = 416 sq ft.
- Ceiling: 12 × 14 = 168 sq ft.
- One door and two windows: 20 + 15 + 15 = 50 sq ft.
- Walls only with 10% waste: (416 − 50) × 1.10 = 402.6 sq ft, which is 12.58 sheets of 4 × 8, so 13.
- Walls and ceiling with 10% waste: (416 + 168 − 50) × 1.10 = 587.4 sq ft, which is 18.36 sheets, so 19.
| What you hang | Waste | 4 × 8 sheets | 4 × 12 sheets |
|---|---|---|---|
| Walls only | 10% | 13 | 9 |
| Walls only | 15% | 14 | 9 |
| Walls and ceiling | 10% | 19 | 13 |
| Walls and ceiling | 15% | 20 | 13 |
Hang it to waste less
- This Old House recommends hanging walls horizontally, which reduces the number of seams, and staggering the joints between rows.
- Keep seams away from the corners of doors and windows. Home Depot says seams there may crack.
- Hang the ceiling first so the wall sheets tuck up against it.
- Use a drywall lift for ceiling panels. This Old House says one rents for about $55 a day at Home Depot.
- This Old House also advises 5/8 in panels when joists are 24 in apart, since thinner board can sag over the wider span.
What the sheet count leaves out
- Screws, joint tape and joint compound.
- Corner bead for outside corners.
- Special board such as moisture-resistant panels in bathrooms or fire-rated board where code requires it.
Common mistakes
- Forgetting the ceiling, which adds six sheets in the example above.
- Choosing 4 × 12 sheets that will not fit up the stairs or around a turn.
- Buying exactly the calculated count with no waste allowance.
- Mixing up board thickness for walls and ceilings.
Calculators for this job
These calculators do the arithmetic from this guide. Each card shows the result for a typical project; open one to enter your own measurements.
Frequently asked questions
How many sheets of drywall for a 12 × 14 room?
With 8 ft walls, one door and two windows, it takes 13 sheets of 4 × 8 for the walls alone and 19 sheets with the ceiling, at 10% waste. With 4 × 12 sheets that is 9 and 13.
How much does a sheet of drywall cover?
A 4 × 8 ft sheet covers 32 sq ft and a 4 × 12 ft sheet covers 48 sq ft, according to Family Handyman.
Is it better to hang drywall horizontally or vertically?
This Old House recommends horizontal installation for walls because it reduces seams and makes them less noticeable. Vertical works better on very tall walls or when you are working alone.
How much waste should I allow for drywall?
Plan on about 10% for a simple room and 15% for rooms with many openings or angles.
Sources
- Family Handyman, How to Hang Drywall Like a Pro
- Family Handyman, 10 Tips for Better Drywall Taping
- This Old House, How To Hang Drywall
- This Old House, How To Hang Drywall on a Ceiling
- The Home Depot, How to Hang Drywall