How this calculator works
We total the wall area (perimeter × height) and, if you tick it, the ceiling. After adding a waste allowance, we divide by the area of one sheet and round up. Fasteners and finishing supplies are scaled to the area: roughly one screw per square foot, about 0.37 feet of tape per square foot, and about a gallon of joint compound per 100 ft².
Worked example: a 12 × 12 ft room with 8 ft ceilings has 384 ft² of walls and 144 ft² of ceiling, 528 ft² in all. With 10% waste that is 581 ft², which is 19 sheets of 4 × 8 ft.
Tips before you buy
- Hang the ceiling first, then the walls. Run sheets horizontally on walls so there are fewer, shorter seams.
- 4 × 12 ft sheets have fewer seams, which means less taping, but they are heavy and awkward to handle for one person.
- For bathrooms, use moisture-resistant (green or purple board) and cement board in wet areas. In garages and near furnaces, check fire-rated requirements (5/8 in Type X).
- Standard thickness is ½ in for walls and ceilings under typical joist spacing. 5/8 in is used for fire ratings and sagging-prone ceilings.
Quick answers by size
Tools & materials for this project
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Frequently asked questions
How many sheets of drywall do I need for a 12x12 room?
About 19 sheets of 4 × 8 ft for the walls and ceiling, including 10% waste. Without the ceiling, about 14 sheets.
How much joint compound do I need?
As a rule of thumb about 1 gallon per 100 ft² of drywall for taping and three coats, so a 4.5 gallon box covers roughly 450 ft².
Should I use 4x8 or 4x12 sheets?
Longer sheets mean fewer seams and less finishing, but they are heavier. Use 4 × 8 ft if you are working alone or in tight spaces.
Related calculators & guides
Estimates only. Results assume standard materials and simple shapes. Supplier products vary, and the final call on quantity, structure and safety is yours. Check your local code and your supplier's guidance before ordering.