Drywall Calculator
How many drywall sheets a room needs, with openings deducted and your own sheet size. Screws, tape and compound are left out on purpose.
Switching units keeps your measurements. Nothing is reset.
What are you boarding?
Doors and windows
No openings yet. Without any, the full wall area is painted.
Your sheets
Waste allowance
10% covers cuts around openings and the offcuts that cannot be reused.
Offcuts, breakages, pattern matching and the occasional damaged piece all mean you use more material than the bare area. Keeping a few spare pieces for future repairs is also normal.
This is a planning allowance, not a rule. Adjust it for your layout, your material and your own tolerance for a second trip to the store.
Estimated cost
Cost uses the price you enter. This product never shows invented market prices.
Your result appears here
Enter your measurements to see how much material to buy.
How to use this calculator
- 1
Enter the room as length, width and wall height, and tick the ceiling if you are boarding that too.
- 2
Add doors and windows with a count. Whether to deduct them at all is a judgement: see the guidance below.
- 3
Pick a sheet size, or type your own. Longer sheets give fewer joints to tape but are much harder to lift alone.
- 4
Adjust the waste allowance, then add a price per sheet if you want a cost.
A worked example
A 12 ft × 15 ft room with 8 ft walls and the ceiling boarded, one door and two windows deducted, in 4 ft × 8 ft sheets with a 10% allowance:
Measured area
567.8 ft²567.8 ft²
Add the waste allowance
567.8 ft² × 1.1624.5 ft²
Divide by the coverage of one package
624.5 ft² ÷ 32 ft²19.52
Round up to whole packages
round up 19.5220
Coverage you are buying
20 × 32 ft²640 ft²
You will need
20 sheets
This example is produced by running the calculator above, so it always matches what the tool does.
The formula
Wall area is the room perimeter multiplied by the wall height, plus the ceiling if included. Openings are deducted from that. The waste allowance is applied, and the result is divided by the area of one sheet and rounded up. A 4 ft × 8 ft sheet is 32 square feet.
Boarding out
Deducting openings can leave you short
Sheets are cut around openings, and the piece removed for a window is usually unusable. Many people deliberately do not deduct small openings, and treat the deduction as a rough saving on large ones only.
Sheet length is a handling decision
Twelve foot sheets mean far fewer butt joints to tape and finish, which is the slow part of the job. They are also awkward to carry up a staircase alone. The count changes with the size, so try both.
Accessories are not a fixed ratio
Screws, tape and compound depend on how you lay the sheets, how many joints result and what finish level you are working to. This calculator gives you sheets and stops there rather than inventing a ratio.
Common questions
- How many sheets of drywall do I need?
- Divide the area to board by the area of one sheet and round up, after adding an allowance for cuts. A 4 ft by 8 ft sheet covers 32 square feet, so 500 square feet of wall needs about 18 sheets with a 10% allowance.
- Should I subtract doors and windows?
- For large openings, yes. For a standard door and a couple of windows, many people do not, because the offcuts are rarely reusable. Both approaches work above.
- How much joint compound and tape will I need?
- This calculator does not estimate them, because the honest answer depends on your sheet layout and finish level rather than on floor area. Work out your sheet count first, then ask your supplier based on the number of joints.