Drywall Calculator

Please fill in the required fields with values greater than 0.
–sq ft to cover
–sheets needed
–screws (approx.)
–estimated cost

Estimate only. Sheet layout and cut-offs vary, so check with your supplier.

How to use this calculator

Enter the room size and wall height and choose whether to drywall the ceiling. Add doors and windows, pick the sheet size and press Calculate to see how many sheets you need.

The formula

Area = walls (2 × (length + width) × height) + ceiling (length × width) − doors and windows
Sheets = area × (1 + waste) ÷ sheet area
Screws are about 1 per square foot of sheet.

Example: A 12 ft × 10 ft room with 8 ft walls, a ceiling, 1 door and 2 windows has 422 sq ft to cover. With 10% waste and 4 × 8 ft sheets you need 15 sheets.

Planning your drywall project

The calculator adds up wall and ceiling area, subtracts doors and windows, adds a waste allowance and divides by the sheet size you chose. The result is the number of full sheets to buy. It also gives a rough screw count, at about one screw per square foot of board.

A worked example

A 12 by 10 foot room with 8 foot walls has 352 square feet of wall and 120 square feet of ceiling. After subtracting one door and two windows, about 422 square feet remain. Add 10% for waste and divide by 32 square feet per 4 by 8 sheet, and you need 15 sheets. At one screw per square foot of sheet, that is about 480 screws.

What changes the sheet count

  • Sheet size. Longer 4 by 12 sheets cover more and mean fewer seams, but the count of full sheets may not drop much in small rooms.
  • Wall height. Walls taller than 8 feet often need a full sheet plus a strip, which raises waste.
  • Openings. Many doors and windows mean more cutting. Some pros skip subtracting small openings and keep the extra as spare.
  • Room shape. Closets, soffits and angled walls add cuts and offcuts. Use 15% waste for complex rooms.

Tips and common mistakes

  • Hang ceilings first, then walls, so the wall sheets help support the ceiling edges.
  • Stagger the end joints so seams do not line up from row to row.
  • Use moisture-resistant board in bathrooms and laundry areas, and cement board behind tile in wet zones.
  • Do not forget corner bead for outside corners and enough joint compound and tape for every seam.
  • Avoid placing seams right at the corners of doors and windows, where cracks often start.

Cost and planning

Enter a price per sheet to estimate board cost. Then add screws, tape, compound, corner bead and sanding supplies, which can add noticeably to the total. Sheets are heavy, and a 4 by 12 sheet can be hard for one person to carry, so plan for help, or rent a drywall lift for ceilings. Many suppliers deliver and stack sheets inside the room for a fee. Fire-rated walls, such as between a garage and the house, may need specific board types, so check local building codes before you buy.

Frequently asked questions

How many sheets of drywall do I need?
Divide the wall and ceiling area by the sheet area, add 10 percent for waste and round up.
What size drywall sheet is best?
4 by 8 ft sheets are easy to carry. Longer 4 by 12 ft sheets mean fewer joints but are heavier and harder to handle.
How thick should drywall be?
Half inch (12.7 mm) is common for walls. Use 5/8 inch for ceilings and fire-rated walls.
How many screws do I need per sheet?
About 32 screws for a 4 by 8 ft sheet, spaced about 12 to 16 inches apart.
Do I need joint compound and tape too?
Yes. You need tape and joint compound for every seam and screw head. Ask your supplier for the right amount for your area.
How much does it cost to drywall a room?
Material cost depends on sheet count and local prices. Multiply your sheet count by the price per sheet, then add the cost of screws, tape, compound and corner bead. If you hire the work out, labor for hanging, taping and finishing can cost more than the board itself. Get two or three local quotes before you decide.
Should drywall be hung horizontally or vertically?
On most residential walls, horizontal hanging is common. It usually means fewer and shorter seams, and the seams sit at a comfortable height for finishing. Vertical hanging can work better on walls taller than 8 feet or on narrow walls. Some local codes and fire-rated assemblies specify orientation, so check before you start.
How long does drywall mud take to dry?
Standard premixed joint compound usually needs about 24 hours per coat, longer in cool or humid rooms. Setting-type compound, sold as a powder, hardens by chemical reaction in a set time printed on the bag, such as 20, 45 or 90 minutes. Most walls need three coats plus sanding, so plan for several days.