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Drywall Calculator

Find how many drywall sheets a wall or ceiling needs, with a waste allowance, plus optional joint compound and screw estimates from your own rates.

What this tool does

Find how many drywall sheets a wall or ceiling needs, with a waste allowance, plus optional joint compound and screw estimates from your own rates. You fill in these fields: Surface area to cover, Sheet size, Waste allowance, Joint compound coverage (optional), and Screws per square foot (optional). Some fields are optional. It shows sheets to buy, area with waste, area the sheets cover, joint compound (estimate), and screws (estimate).

Inputs

  • Surface area to cover (sq ft): A number. Must be at least 0. Total area of the walls and ceiling to board. Subtract doors and windows yourself if you want to.
  • Sheet size: Choose one: 4 ft by 8 ft (32 sq ft), 4 ft by 10 ft (40 sq ft), 4 ft by 12 ft (48 sq ft). Starts as 4 ft by 8 ft (32 sq ft).
  • Waste allowance (%): A number. Accepts 0 to 100. Starts at 10 %. Extra material for cuts and mistakes. The 10 is only an example; replace it with your own figure.
  • Joint compound coverage (optional) (sq ft per gallon): A number. Must be at least 0. Enter the coverage printed on your compound's label. Leave empty to skip.
  • Screws per square foot (optional) (screws per sq ft): A number. Must be at least 0. Enter the rate from your fastening schedule or screw maker. Leave empty to skip.

How to use

  1. Enter the surface area to cover in sq ft.
  2. Choose 4 ft by 8 ft (32 sq ft), 4 ft by 10 ft (40 sq ft), or 4 ft by 12 ft (48 sq ft) for "Sheet size".
  3. Enter the waste allowance as a percentage.
  4. Enter the joint compound coverage (optional) in sq ft per gallon.
  5. Enter the screws per square foot (optional) in screws per sq ft.
  6. Read the result: sheets to buy, area with waste, area the sheets cover, joint compound (estimate), and screws (estimate). It appears once every required field has a valid value.

Worked examples

Example 1. Inputs:

  • Surface area to cover: 320 sq ft
  • Sheet size: 4 ft by 8 ft (32 sq ft)
  • Waste allowance: 10%

Results:

  • Sheets to buy: 11 (rounded up from 11)
  • Area with waste: 352 sq ft
  • Area the sheets cover: 352 sq ft

How this is worked out: Area with waste = 320 * 1.10 = 352 sq ft. Sheet area = 4 * 8 = 32 sq ft. 352 / 32 = 11 sheets exactly, so 11. Covered = 11 * 32 = 352.

Example 2. Inputs:

  • Surface area to cover: 330 sq ft
  • Sheet size: 4 ft by 8 ft (32 sq ft)
  • Waste allowance: 0%

Results:

  • Sheets to buy: 11 (rounded up from 10.31)
  • Area with waste: 330 sq ft
  • Area the sheets cover: 352 sq ft

How this is worked out: No waste: 330 sq ft. 330 / 32 = 10.3125, a part sheet cannot be bought so round up to 11. Covered = 11 * 32 = 352.

Example 3. Inputs:

  • Surface area to cover: 425 sq ft
  • Sheet size: 4 ft by 10 ft (40 sq ft)
  • Waste allowance: 15%
  • Joint compound coverage (optional): 150 sq ft per gallon
  • Screws per square foot (optional): 1.1 screws per sq ft

Results:

  • Sheets to buy: 13 (rounded up from 12.22)
  • Area with waste: 488.75 sq ft
  • Area the sheets cover: 520 sq ft
  • Joint compound (estimate): 3.3 gallons (Area with waste divided by the coverage you entered)
  • Screws (estimate): 538 (Area with waste times the rate you entered, rounded up)

How this is worked out: Reviewer vector; the rates are example inputs. Area with waste = 425 * 1.15 = 488.75 sq ft (waste applied once). Sheet area = 4 * 10 = 40. 488.75 / 40 = 12.21875, round up to 13. Covered = 13 * 40 = 520. Compound = 488.75 / 150 = 3.2583333 gallons. Screws = 488.75 * 1.1 = 537.625, round up to 538. Both use 488.75, not 425 and not 520.

Example 4. Inputs:

  • Surface area to cover: 320 sq ft
  • Sheet size: 4 ft by 8 ft (32 sq ft)
  • Waste allowance: 10%
  • Joint compound coverage (optional): 0 sq ft per gallon

Results:

  • Sheets to buy: 11 (rounded up from 11)
  • Area with waste: 352 sq ft
  • Area the sheets cover: 352 sq ft

How this is worked out: A coverage of 0 and an empty screw rate both mean skip: the optional amounts are 0 and their cards stay hidden. Sheets as in the first vector, 352 / 32 = 11.

Limitations

  • The sheet count is simple area arithmetic. It does not plan cuts, seams or layout, so an awkward room can need more sheets than the count shows.
  • Joint compound and screws are estimates from the rates you type, applied to the area with waste. Check them against the product label before buying.
  • The tool does not subtract doors or windows, and it does not include tape, corner bead or primer.

FAQs

Q: How does the calculator work out the number of sheets?
A: It adds your waste allowance to the area, divides by the area of one sheet (width times length), and rounds up to a whole sheet. For example, 320 sq ft with 10 percent waste is 352 sq ft, which is exactly 11 sheets of 4 by 8 feet.
Q: Should I measure the area of doors and windows?
A: The tool uses the area you enter and does not subtract openings. Subtract them yourself before entering the area if you want to leave them out, or leave them in as extra allowance.
Q: Where do the joint compound and screw amounts come from?
A: Only from the rates you enter. Coverage and fastener spacing vary by product and by local practice, so the tool has no built-in figure. Use the coverage printed on your compound's label and the spacing in your fastening schedule.
Q: What waste allowance should I use?
A: The field starts at 10 percent as an example. Use a higher figure for rooms with many cuts or odd angles, and a lower one for simple rooms. You can enter 0 or more.

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