How to calculate drywall sheets
- Multiply the room perimeter by the wall height to get the wall area.
- Add the ceiling (length × width) if you are covering it.
- Subtract doors and windows, add 10 to 15 percent for waste, and divide by the area of one sheet.
sheets = (wall area + ceiling − openings) × (1 + waste %) ÷ sheet area
Worked example
A 14 × 12 ft room with 8 ft walls has 416 sq ft of wall. Remove one door and two windows (50 sq ft) and add the 168 sq ft ceiling: 534 sq ft. With 10 percent waste that is 587 sq ft, or 19 sheets of 4 × 8.
Which sheet size?
| Size | Area | Good for |
|---|---|---|
| 4 × 8 ft / 1200 × 2400 mm | 32 sq ft / 2.88 m² | Working alone, small rooms, tight stairways |
| 4 × 10 ft | 40 sq ft | 9 ft walls hung vertically |
| 4 × 12 ft / 1200 × 3600 mm | 48 sq ft / 4.32 m² | Fewer seams on long walls and ceilings; needs two people |
Fewer joints mean less taping and sanding, so larger sheets can save finishing time even if they are harder to carry.
Thickness
Half-inch (about 12.5 or 13 mm) board is the usual choice for interior walls. Thicker or fire-rated board is required in some places, such as walls between a garage and a house. Requirements vary by country and local code, so check before you buy.
Screws, tape and compound
Plan on roughly one screw per square foot of board, which is about 32 per 4 × 8 sheet. Joint tape and compound depend on how many seams and corners you have; the joint compound calculator gives a rule-of-thumb estimate from the board area.
Frequently asked questions
How many sheets of drywall for a 12 × 12 room?
With 8 ft walls, a 12 × 12 room has 384 sq ft of wall. That is 12 sheets of 4 × 8 before waste, or 14 sheets with 10 percent extra. Add 5 more for the ceiling.
Should I subtract windows and doors?
Many installers hang full sheets over small openings and cut them out, so they subtract only large openings. If you do that, set doors and windows to 0.
Do I hang drywall horizontally or vertically?
On standard 8 or 9 ft walls, many installers hang sheets horizontally because it usually leaves fewer joints. Follow local practice and code.
Is plasterboard the same as drywall?
Yes. Drywall is the common US and Canadian term; plasterboard and gyprock are common in Australia and the UK.