Drywall Calculator
Estimate drywall sheet count for room walls and an optional ceiling, with openings and waste allowance.
How to Use
- Enter the room length, width and wall height, then choose feet or meters.
- Choose whether the ceiling should be included in the estimate.
- Enter the combined area of doors, windows and other openings you want to subtract. Leave it at 0 if you do not want to subtract openings.
- Enter the width and length of one drywall sheet. The defaults are 4 ft × 8 ft, but change them to match the boards you will actually buy.
- Set an extra-material allowance for cuts, breakage and layout waste. The result rounds the sheet count up to the next whole sheet.
Formula
- Wall area
- wall_area = 2 × (room_length + room_width) × wall_height
- Ceiling area
- ceiling_area = room_length × room_width (when included)
- Net area
- net_area = wall_area + ceiling_area − openings_area
- Purchase area
- purchase_area = net_area × (1 + extra_percentage ÷ 100)
- Sheet count
- sheets = ceil(purchase_area ÷ sheet_area)
Worked Example
A 12 ft × 10 ft room with 8 ft walls, 40 ft² of openings, 4 × 8 ft sheets and 10% extra material.
- Wall area: 2 × (12 + 10) × 8 = 352 ft².
- Subtract openings: 352 − 40 = 312 ft².
- Add 10% allowance: 312 × 1.10 = 343.2 ft².
- One 4 × 8 sheet covers 32 ft².
- 343.2 ÷ 32 = 10.725, so round up to 11 sheets.
Result: Estimated sheets: 11
About This Tool
What this tool does
This calculator estimates drywall coverage for the four walls of a rectangular room, with an optional ceiling. It can subtract a combined openings area and then convert the remaining coverage into a whole-sheet quantity using the board size you enter.
When to use it
Use it for preliminary material takeoffs, shopping lists and budgeting when the room is reasonably rectangular and you already know which drywall board size you plan to purchase.
What the result means
The sheet count is rounded up because partial sheets cannot normally be purchased as fractions. The area lines let you compare the estimate with plans, supplier quantities or your own takeoff.
Assumptions & limitations
The room is treated as a rectangular perimeter with one uniform wall height. The estimate is based on surface area, not an optimized sheet-layout plan, so seams, orientation, staggered joints and cut reuse are not modeled. The tool does not select board thickness, fire rating, moisture rating, fasteners or framing details; follow the project specification and applicable code.