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HowMuchDoINeed.fyi

Drywall Calculator

How much drywall do you need?

Measurements

Units
What to measure

8 ft is standard; many newer homes have 9 ft

Sheet size
Options · Extra 10%

Covers cut-offs around doors, windows and outlets. Use 15% for rooms with many angles.

You need

Enter room length, room width and wall height to see how much to buy.

Example: a 12 × 12 ft room with 8 ft walls, ceiling included

  1. Walls: 2 × (12 + 12) × 8 = 384 sq ft. Ceiling: 12 × 12 = 144 sq ft. Total: 528 sq ft.
  2. Add 10% for cut-offs: 580.8 sq ft.
  3. One 4 × 8 sheet covers 32 sq ft: 580.8 ÷ 32 = 18.2, so buy 19 sheets.
  4. Finishing: about 5.3 gallons of joint compound (two 4.5-gal buckets), 200 ft of tape and 550 screws.

How it's calculated

  1. Wall area = perimeter × height, where the perimeter is 2 × (length + width).
  2. Add the ceiling (length × width) if you're covering it.
  3. Sheets = total area × (1 + extra %) ÷ area of one sheet, rounded up.
  4. Joint compound, tape and screws are estimated from the board area.

Assumptions

  • Doors and windows aren't subtracted — the cut-outs are usually waste anyway.
  • 10% extra by default for cut-offs.
  • Finishing estimates: about 1 gallon of all-purpose joint compound per 100 sq ft, 370 ft of paper tape per 1,000 sq ft, and one screw per sq ft of board.

Frequently asked questions

How many sheets of drywall do I need for a 12 × 12 room?

With 8 ft walls, about 14 sheets of 4 × 8 for the walls (384 sq ft plus 10% extra) and 5 more for the ceiling.

What size drywall should I buy?

4 × 8 sheets are the easiest to carry and fit in most vehicles. 4 × 10 and 4 × 12 sheets mean fewer seams to tape on long walls and tall ceilings, but they're heavy and usually need two people.

What thickness of drywall do I need?

1/2 in is standard for interior walls. 5/8 in is common on ceilings and required for fire-rated walls, such as between a garage and the house — check your local code. 1/4 in is used to resurface existing walls.

Should I subtract doors and windows?

Usually not. Pros hang full sheets and cut the openings out, so those pieces become waste. Subtract only very large openings like sliding or garage doors — use Wall(s) mode and enter the reduced width.

How much joint compound and tape do I need?

Roughly 1 gallon of all-purpose compound per 100 sq ft of drywall for taping and three coats, and about 370 ft of tape per 1,000 sq ft. The calculator adds both to your shopping list.

Which drywall should I use in a bathroom?

Moisture-resistant board (often green or purple) in bathrooms and laundry rooms, and cement board behind tile in showers and tub surrounds.