Short answer
A 16x20 living room with 9-foot ceilings needs 29 sheets of 4×8 drywall. That figure covers all four walls plus the ceiling, deducts one standard door and three windows, and rounds up to account for cutting waste. The total drywall area works out to 902 sq ft.
How this calculator works
The drywall calculator takes six inputs for a room — length, width, ceiling height, number of doors, number of windows, and whether you're including the ceiling — and produces a sheet count you can bring straight to the lumber yard.
Wall area
The wall perimeter for a 16×20 room is (16 + 20) × 2 = 72 linear feet. Multiply that by the 9-foot ceiling height and you get 648 sq ft of gross wall area.
Deductions for openings
The calculator subtracts 21 sq ft per door (a standard 3×7 rough opening) and 15 sq ft per window (a standard 3×5 opening). With 1 door and 3 windows:
- 1 door × 21 = 21 sq ft
- 3 windows × 15 = 45 sq ft
- Total deducted: 66 sq ft
Net wall area: 648 − 66 = 582 sq ft
Ceiling area
With include_ceiling = 1, the calculator adds length × width = 16 × 20 = 320 sq ft for the ceiling.
Total area and sheet count
582 (walls) + 320 (ceiling) = 902 sq ft total
A standard 4×8 sheet covers 32 sq ft. Divide 902 by 32 to get 28.2 sheets. The formula uses ceil() to round up to 29 sheets — you can't buy a fraction of a sheet, and that fractional overage also serves as your cut-waste buffer.
Secondary outputs
The calculator extends the sheet count into a full material list:
Drywall screws: At 30 screws per sheet, 29 sheets requires 870 screws (1-5/8 inch coarse thread). This rate assumes screws every 8 inches along studs and 12 inches on ceiling joists — the minimum for code-compliant fastening.
Joint tape: The estimate of 70 linear feet of tape per sheet accounts for the seams between sheets plus inside corners. For 29 sheets that's 2,030 linear feet. Buy mesh tape in 500-ft rolls; you'll need four to five rolls.
Joint compound: The rule of thumb is one 5-gallon bucket per 8 sheets. For 29 sheets, round up to 4 buckets. All-purpose compound works for taping and topping coats, though some finishers prefer a lightweight topping compound for the final coat because it sands more easily.
What the calculator doesn't cover
The formula assumes rectangular rooms with flat ceilings and standard-height openings. It won't account for:
- Vaulted or tray ceilings — calculate those slopes as separate triangles and add the area manually
- Arched openings — deduct the arch area the same way you would a window
- Closets or alcoves inside the room — measure those walls separately and add them in
- Specialty board like moisture-resistant drywall in bathrooms or soundboard in media rooms
For a 16×20 living room, none of those exceptions typically apply, and 29 sheets is the right number to order.
Recommended materials
For a 29-sheet job, the two non-negotiables are consistent panel thickness and enough fasteners to not run short mid-hang. Half-inch UltraLight board is noticeably easier to handle solo on the ceiling than standard-weight panels and holds screws just as well.
- USG Sheetrock UltraLight 1/2 inch drywall (4x8) — lighter than standard 1/2-inch board, cuts and finishes identically
- Grip-Rite 1-5/8 inch drywall screws (5 lb box) — coarse thread bites into wood framing without stripping; buy two boxes for this job
- USG Sheetrock all-purpose joint compound (5 gallon) — works for taping, second coat, and finish; one consistent product across all three coats simplifies cleanup
- Saint-Gobain ADFORS FibaTape mesh joint tape (500 ft) — self-adhesive mesh positions faster than paper tape on flat seams; buy four rolls for this project
FAQ
How many sheets of drywall for a 16x20 living room with 9-foot ceilings? You need 29 sheets of 4x8 drywall for a 16x20 room with 9-foot ceilings, 1 door, and 3 windows. That figure already accounts for a 10% waste factor built into the rounding.
Does the calculator include the ceiling? Yes, by default this calculator adds the ceiling area. For a 16x20 room that's 320 sq ft of ceiling drywall on top of the 582 sq ft of net wall area. Turn ceiling off if you're only drywalling walls.
What waste factor is used? The formula rounds up to the next whole sheet, which effectively builds in a roughly 10% waste buffer. That covers standard cutting waste at corners, outlets, and seams.
How much does a standard door opening subtract? The calculator deducts 21 sq ft per door opening, which matches a standard 3-ft-wide by 7-ft-tall rough opening. Custom or oversized doors will have larger openings.
How much does a window opening subtract? Each window deducts 15 sq ft, sized for a typical 3×5 residential window. Bay windows or picture windows are larger — measure those individually and adjust the count.
How many drywall screws do I need for 29 sheets? Plan on 870 screws (1-5/8 inch) for 29 sheets at the standard rate of 30 screws per sheet. A 5 lb box typically holds around 500–550 screws, so buy two boxes.
How much joint compound do I need? For 29 sheets you'll need approximately 4 five-gallon buckets of all-purpose joint compound. That estimate covers taping, topping, and finish coats on all seams.
How much joint tape do I need? The calculator estimates 2,030 linear feet of joint tape for 29 sheets. A 500-ft roll of mesh tape means you'll need four to five rolls.
Should I use 1/2-inch or 5/8-inch drywall for a living room? Half-inch drywall is standard for most interior residential walls and ceilings. Use 5/8-inch Type X if the wall is adjacent to a garage or requires a fire-rated assembly.
Can I hang 4x8 sheets horizontally to reduce seams? Yes, and on 9-foot walls it's actually preferred. Running sheets horizontally means the horizontal seam lands at 4 feet up the wall — easier to tape and less visible than a vertical butt joint.
What thickness drywall is standard for ceilings? Half-inch drywall works for ceilings with framing 16 inches on center. If your ceiling joists are 24 inches on center, step up to 5/8-inch to prevent sag over time.