Drywall Calculator
How many drywall sheets you need for a room or a run of walls, minus doors and windows, with the ceiling if you like.
Your walls
Filled in with example values. Replace them with your own.
Adds the ceiling area (length × width).
Sheets
Cut pieces around doors, windows and corners are partly wasted. On by default.
Results update as you type.
Result
Drywall sheets: 15 of 4 ft × 8 ft (including 10% extra)
Sheets to buy
15sheets
- Wall area
- 352 ft²
- Doors (1)Not covered
- − 21 ft²
- Windows (2)Not covered
- − 32 ft²
- Ceiling
- + 120 ft²
- Area to cover
- 419 ft²
- One sheet covers
- 32 ft²
- Sheets before roundingIncluding extra
- 14.4
How it’s calculated
Wall area
2 × (12 ft + 10 ft) × 8 ft = 352 ft²
Minus doors and windows
352 ft² − 53 ft² = 299 ft²
Plus the ceiling
299 ft² + 12 ft × 10 ft = 419 ft²
Plus 10% extra
419 ft² × 1.1 = 460.9 ft²
Sheets, rounded up
460.9 ft² ÷ 32 ft² = 14.4 = 15 sheets
How the drywall calculator works
Enter the room’s length, width and wall height, or switch to “Walls by length” to cover only some walls. The calculator works out the wall area, subtracts doors and windows, adds the ceiling if you choose, adds a percentage for offcuts and divides by the area of one sheet. The result is rounded up to whole sheets.
Drywall is also called plasterboard, gypsum board or wallboard; the calculation is the same.
The formula
Wall area = 2 × (Length + Width) × Height
Area to cover = Wall area − Doors and windows + Ceiling
Sheets = Area to cover × (1 + Extra % ÷ 100) ÷ Sheet area, rounded up
Worked example
A room 12 × 10 ft with 8 ft walls, one 3 × 7 ft door, two 4 × 4 ft windows and the ceiling, using 4 × 8 ft sheets and 10% extra:
- Wall area: 2 × (12 + 10) × 8 = 352 ft²
- Doors and windows: 21 + 2 × 16 = 53 ft², leaving 299 ft²
- Ceiling: 12 × 10 = 120 ft², so 419 ft² to cover
- With 10% extra: 419 × 1.1 = 460.9 ft²
- Sheets: 460.9 ÷ 32 = 14.4, rounded up to 15 sheets
Units, assumptions and limitations
- Conversions use exact definitions: 1 inch = 25.4 mm, 1 foot = 12 inches.
- The room is a rectangle with walls of one height. Sloped ceilings and gable walls need to be measured separately.
- The estimate is based on area. It does not plan where each sheet goes or where it is cut.
- One face of each wall is counted.
- Which board type a wall needs (for example in wet rooms or for fire separation) depends on local building rules. This calculator does not recommend one.
Frequently asked questions
What size drywall sheets should I use?
Choose the size you plan to buy. Larger sheets mean fewer joints to tape but are heavier to lift, and they need to fit through doors and stairways. The calculator lists some common sizes and accepts any other size.
Why does the calculator subtract doors and windows?
Those areas are not covered, so leaving them out gives a closer estimate. If you plan to hang full sheets over openings and cut them out afterwards, leave the openings empty or increase the extra percentage.
How do I cover only some walls?
Switch to “Walls by length” and enter the total length of the walls you want to cover, added together. The ceiling option is only available for a whole room.
Does it count both sides of a wall?
No. It counts one face of each wall. For a new partition covered on both sides, enter its length twice in the total wall length.
Does it include screws, tape or joint compound?
No. How much fixings and finishing material you need depends on the products and on how the sheets are hung, so check the manufacturer’s guidance.