Drywall Calculator
Calculate how many drywall sheets you need for a room, plus joint compound, tape, screws and an estimated material cost.
Formulas shown on this page · Last reviewed October 2026
How the drywall calculator works
The tool adds up wall area and, if selected, the ceiling, then subtracts doors (21 sq ft) and windows (15 sq ft). Waste is added before dividing by the sheet area, and the result is rounded up to whole sheets. Compound, tape and screws are based on the net area.
area = 2 × (L + W) × height + (L × W if ceiling) − openings
sheets = area × (1 + waste) ÷ sheet area, rounded up
compound = area × 0.01 gal (4.5 gal bucket ≈ 450 sq ft)
tape = area × 0.37 ft · screws ≈ 1 per sq ft of board
Drywall sheet sizes
| Sheet | Area | Screws | Weight, 1/2 in |
|---|---|---|---|
| 4 × 8 ft | 32 sq ft | ~32 | ~54 lb |
| 4 × 10 ft | 40 sq ft | ~40 | ~68 lb |
| 4 × 12 ft | 48 sq ft | ~48 | ~82 lb |
Practical tips
- On an 8 ft wall, hang 4×8 sheets horizontally or 4×12 sheets to cut the number of butt joints, which are the hardest seams to finish.
- Hang the ceiling first, then the upper wall sheets, then the lower ones.
- Buy an extra bucket of compound if you are new to finishing – sanding and a third coat use more than you expect.
- Corner bead, primer and sandpaper are not included in the cost estimate. Sheet prices vary by region and thickness.
Frequently asked questions
How many sheets of drywall do I need for a 12×12 room with 8 ft ceilings?
Walls are 2 × (12 + 12) × 8 = 384 sq ft and the ceiling is 144 sq ft, for 528 sq ft. Subtracting one door (21 sq ft) and two windows (30 sq ft) leaves 477 sq ft. With 10% waste that is 524.7 sq ft, or 17 sheets of 4×8 (32 sq ft each).
How much joint compound do I need?
This calculator uses 0.01 gallon per square foot of drywall, about 1 gallon per 100 sq ft, which covers taping plus two finish coats. A 4.5 gallon bucket therefore finishes about 450 sq ft, or roughly 14 sheets of 4×8. The 477 sq ft room above needs 4.8 gallons, so 2 buckets.
Should I use 1/2 inch or 5/8 inch drywall?
Use 1/2 inch for most residential walls and ceilings with joists 16 inches apart. 5/8 inch is required for fire-rated assemblies such as garage walls shared with living space, and sags less on ceilings with 24 inch spacing. A 4×8 sheet weighs about 54 lb at 1/2 inch and about 70 lb at 5/8 inch.
How many screws and how much tape per sheet?
Plan on about 32 screws per 4×8 sheet, one per square foot, spaced 12 inches apart on ceilings and 16 inches on walls. Paper tape runs about 370 feet per 1,000 sq ft of drywall, so a 250 ft roll covers around 675 sq ft.