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Drywall Calculator

Enter a room’s dimensions to find how many sheets of drywall you need for the walls and, optionally, the ceiling. Doors and windows are subtracted, waste is added, and you can choose 4×8, 4×10 or 4×12 sheets.

Quick examples

Each door subtracts 21 sq ft (3 × 7 ft).

Each window subtracts 15 sq ft (3 × 5 ft).

%

10% covers offcuts; use 15% for rooms with many corners or angles.

$
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Sheets needed19
Area to cover
533 ft²
Sheet cost
$285.00

Saved setups

Save a set of inputs you reuse — your usual rate, your loan, your room sizes — and load it back in one tap.

    Your recent calculations

    Results you calculate here are kept on this device so you can come back to them.

      Formula

      Wall area = 2 × (length + width) × height − doors × 21 − windows × 15 (sq ft)
      Total area = wall area + ceiling (length × width) if included
      Sheets = total area × (1 + waste %) ÷ sheet area, rounded up

      How to use it

      1. Enter the room’s length, width and wall height.
      2. Enter the number of doors and windows.
      3. Tick the ceiling box if you are boarding it too.
      4. Choose a sheet size and waste allowance, then read the sheet count.

      Worked examples

      A 14 × 12 ft room with 8 ft walls, one door, two windows and the ceiling, in 4 × 8 sheets

      Area to cover
      533 ft²
      Sheets needed
      19
      Sheet cost
      $285.00

      A 10 × 10 ft room with no openings, walls and ceiling, in 4 × 12 sheets

      Area to cover
      420 ft²
      Sheets needed
      10
      Sheet cost
      $200.00

      Choosing a sheet size

      4 × 8 ft sheets (32 sq ft) are the easiest to carry and fit most rooms with 8 ft ceilings. 4 × 12 ft sheets (48 sq ft) mean fewer joints to tape and are what professionals prefer, but they are heavy and awkward to move alone.

      ½ in board is standard for walls. Ceilings with joists 24 in apart usually call for ⅝ in or sag-resistant ½ in board, and garages and shared walls often require ⅝ in fire-rated (Type X) board by code.

      This is an area estimate

      Dividing area by sheet size is accurate for ordering in most rooms, but it does not plan the layout. Rooms with many short walls, soffits or angled ceilings produce more offcuts, so raise the waste allowance to 15%.

      Questions people ask

      How many sheets of drywall do I need for a 12×14 room?

      With 8 ft walls, one door, two windows and the ceiling there are 533 sq ft to cover. Adding 10% waste, that is 19 sheets of 4 × 8 or 13 sheets of 4 × 12.

      How many square feet does a sheet of drywall cover?

      A 4 × 8 sheet covers 32 sq ft, a 4 × 10 covers 40 sq ft and a 4 × 12 covers 48 sq ft.

      Should I subtract doors and windows?

      For ordering, many installers do not, and treat the openings as their waste allowance. This calculator subtracts them and adds a separate waste percentage, which comes out much the same.

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