Drywall calculator
This divides the area you enter by a sheet's area and rounds up. It does not read a plan or deduct openings for you — subtract large openings yourself, and confirm the count against the actual room before you order.
Enter the size of a wall or ceiling and how many surfaces of that size you have, pick a sheet, and the tool totals the area, divides by the sheet area, adds waste and rounds up to whole sheets. That rounded number is what you buy.
Worked example
A room with four 12 ft × 8 ft walls is 4 × 96 = 384 square feet. Using 4×8 sheets at 32 ft² each, that is 384 ÷ 32 = 12 sheets before waste. Add 10% and round up and you are buying 14 sheets. Switch to 4×12 sheets and the same wall area needs 9 before waste, 10 after.
The formula
sheets = (total area × (1 + waste)) ÷ sheet area, rounded up
Total area is the surface length times height times the number of surfaces. Dividing by one sheet's area gives a fractional sheet count; the waste factor covers the offcuts, and rounding up turns it into whole sheets you can actually buy.
Questions
- How many sheets of drywall do I need?
- Work out the total surface area of the walls and ceilings, then divide by the area of one sheet and round up. A 4×8 sheet covers 32 square feet; a 4×12 covers 48. This tool does the division for you once you enter the area and pick a sheet size, and it adds a waste factor for cuts.
- What size drywall sheet should I use?
- Bigger sheets mean fewer seams to tape, which is faster and looks better, but they are heavier and harder to handle in tight spaces. 4×8 is the easy-to-carry standard; 4×12 is common on long walls and ceilings with a lift or a second pair of hands. Pick the size in the tool and the count adjusts.
- Do I subtract windows and doors?
- You can, but many hangers do not bother for small openings — the offcuts rarely make a full sheet and the waste factor absorbs them. For big openings like a garage door or a wall of glass, subtract them from the area you enter so you are not buying sheets you will never hang.
- How much waste should I allow for drywall?
- Around 10% is typical, which is the default here. Bump it up for a room full of angles, closets and short walls, where you cut more and waste more, and you can trim it down on a big open rectangle where full sheets go up with little offcut.
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