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Drywall Calculator: Sheets, Joint Compound and Screws

Enter the room size, openings and sheet size to get the sheets to buy. Joint compound and screws are estimates based on stated rules of thumb. After switching units, re-enter your measurements.

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Formula

board area = 2 × (length + width) × height − doors × 20 − windows × 15 (+ length × width for the ceiling)
sheets     = round up (board area × (1 + waste%) ÷ sheet area)    4×8 = 32 sq ft, 4×12 = 48 sq ft
compound   = board area × 0.01 US gallon per sq ft
screws     = sheets × sheet area × 1 per sq ft

Worked example

A 12 ft by 10 ft room, 8 ft walls, one door, two windows, ceiling included, 10% waste:

  • Walls 352 − 50 = 302 sq ft; ceiling 120 sq ft; board area 422 sq ft.
  • With waste: 464.2 sq ft ÷ 32 = 14.5, so 15 sheets of 4×8 (or 464.2 ÷ 48 = 9.7, so 10 sheets of 4×12).
  • Compound: 422 × 0.01 = 4.22 gallons.
  • Screws: 15 sheets × 32 = 480 screws.

Assumptions

  • A door is 20 sq ft and a window 15 sq ft; they are deducted from the wall area.
  • Joint compound: about 0.01 US gallon of premixed compound per square foot of board for taping and three coats. Setting-type powders and thick skim coats use more.
  • Screws: about 1 per square foot of board, which is 32 on a 4×8 sheet at roughly 12 in spacing in the field and closer at edges.
  • Joint tape, corner bead and framing are not included. Metric sheets are the same 4×8 and 4×12 ft sizes (1.2192 m wide).

Frequently asked questions

How many sheets of drywall do I need for a 12 by 10 ft room?

With 8 ft walls, one door, two windows and the ceiling, the area is 302 + 120 = 422 sq ft. Add 10% waste for 464.2 sq ft and divide by 32 sq ft per 4×8 sheet: 14.5, so 15 sheets.

Should I use 4x8 or 4x12 sheets?

Longer 4×12 sheets mean fewer butt joints to finish, which saves taping time, but they are heavy and awkward. The same 422 sq ft room needs 10 sheets of 4×12 against 15 of 4×8.

How much joint compound and how many screws are needed?

These are rules of thumb: about 0.01 US gallon of premixed compound per sq ft of board (roughly 5 gallons per 500 sq ft) and about 1 screw per sq ft, or 32 for a 4×8 sheet. For 422 sq ft that is 4.2 gallons and 480 screws for 15 sheets.

How much waste should I allow?

Ten percent covers normal cutting around openings and corners. Use 15% or more for rooms with many angles or when the board is installed in short pieces.

How we calculate

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