How the drywall calculator works
The calculator finds the wall area, takes off doors and windows, adds the ceiling if you choose, and divides by the area of one sheet with an allowance for cuts.
Wall area = 2 × (length + width) × height − 21 sq ft per door − 15 sq ft per window
Sheets = (wall area + ceiling) × (1 + waste) ÷ sheet area
Worked example
A 14 by 12 foot room with 8 foot walls has 416 sq ft of wall. One door and two windows take off 51 sq ft, leaving 365 sq ft. The 168 sq ft ceiling brings it to 533 sq ft. With 10% extra that is 586 sq ft, or 19 sheets of 4 by 8 drywall.
Finishing materials
| Material | Rule of thumb used |
|---|---|
| Screws | About 1 per sq ft of board (32 per 4 by 8 sheet) |
| Ready-mixed joint compound | About 9 gallons per 1,000 sq ft (tape coat plus two finish coats) |
| Paper tape | About 380 ft per 1,000 sq ft, in 250 ft rolls |
| Corner bead | One length per outside corner per 8 ft of wall height |
Compound use varies a lot with skill and finish level, so treat it as a starting point. It is easy to buy another bucket.
Sheet sizes and thickness
| Use | Common choice |
|---|---|
| Interior walls | 1/2 in standard |
| Ceilings | 1/2 in sag-resistant or 5/8 in |
| Bathrooms and laundry | Moisture-resistant board; cement board behind tile in showers |
| Garage walls shared with the house | 5/8 in Type X where your code requires a fire separation |
Before you buy
- Hang the ceiling first, then the walls, so wall sheets support the ceiling edges.
- Hang wall sheets horizontally on 8 foot walls; it usually means fewer seams.
- Check that your vehicle can carry the sheet length, or ask about delivery.
Common questions
How many sheets of drywall do I need for a 12x12 room?
A 12 by 12 room with 8 foot walls has 384 sq ft of wall. Take off one door and one window (36 sq ft), add 10% waste, and you need about 12 sheets of 4 by 8 drywall for the walls, plus 5 more if you hang the ceiling.
Should I use 4x8 or 4x12 sheets?
Longer sheets cover more with fewer joints, so there is less taping. 4 by 8 sheets are lighter and easier to carry and hang alone. Many pros use 4 by 12 on long walls and ceilings.
How much joint compound do I need?
Rules of thumb range widely. This calculator uses about 9 gallons of ready-mixed compound per 1,000 sq ft for taping and two finish coats, which is about one 4.5 gallon bucket per 500 sq ft. Buy one extra if you are learning.
How many screws per sheet of drywall?
About 1 screw per square foot, so roughly 32 for a 4 by 8 sheet. Ceilings and local code may require closer spacing.
What thickness of drywall should I use?
1/2 inch is standard for walls. Ceilings often use 1/2 inch sag-resistant or 5/8 inch board, and 5/8 inch Type X is used where fire-rated walls are required, such as between a garage and the house.