Drywall Calculator
Get the sheet count for any room and the three things people forget to buy with it — screws, joint compound and tape — worked out from the same area.
How to use this calculator
- Measure the room, then decide on the ceiling. Ceilings are boarded first and are the hardest part of the job; include them in the count only if you are doing them.
- Choose the sheet length deliberately. Longer sheets mean fewer butt joints, which are the hardest joints to hide — but 4 × 12 ft sheets weigh around 90 lb and are awkward for one person in a stairwell.
- Keep 10% waste. Cuts around openings, corner offcuts and the odd broken sheet. Go to 15% for a room with many windows, angles or a stairwell.
- Buy the consumables at the same time. The tool gives screws, compound and tape from your area — running out of compound mid-coat means a visible joint where the two batches meet.
The formula
Sheets are simply area divided by sheet area, rounded up:
sheets = ceiling( area × (1 + waste%) ÷ sq ft per sheet )
| Sheet | Coverage | Weight (1/2 in) | Best for |
|---|---|---|---|
| 4 x 8 ft | 32 sq ft | ~55 lb | Tight spaces, solo work |
| 4 x 9 ft | 36 sq ft | ~62 lb | 9 ft walls, vertical hang |
| 4 x 10 ft | 40 sq ft | ~70 lb | Fewer butt joints |
| 4 x 12 ft | 48 sq ft | ~82 lb | Long walls, two people |
The consumables come from standard usage rates:
| Item | Rate used |
|---|---|
| Screws | 32 per sheet; about 320 screws to the pound at 1-1/4 in |
| All-purpose joint compound | About 1 gallon per 100 sq ft, for tape plus 3 coats |
| Joint tape | About 0.4 linear ft per sq ft of board |
Worked example
A 14 × 12 ft room with 8 ft walls, one door, two windows, ceiling included, 4 × 8 ft sheets, 10% waste:
- Walls: 2 × (14 + 12) × 8 = 416 sq ft
- Openings: 21 + 30 = 51 → 416 − 51 = 365 sq ft
- Ceiling: 14 × 12 = 168 → total 533 sq ft
- With 10%: 586 sq ft
- Sheets: 586 ÷ 32 = 18.3 → 19 sheets
- Screws: 19 × 32 = 608, about 1.9 lb
- Compound: 586 ÷ 100 = 5.9 gal, so two 4.5 gal boxes
- Tape: 586 × 0.4 = 235 linear ft
The same room in 4 × 12 ft sheets is 13 sheets instead of 19 — six fewer pieces to handle and far fewer butt joints to hide, at 82 lb each. That is the whole trade-off between the two sizes, and it is worth running both numbers before you load the truck.
Board thickness and type
| Type | Where |
|---|---|
| 1/2 in regular | Standard walls and ceilings on 16 in centres |
| 5/8 in Type X | Fire-rated assemblies, garage ceilings, 24 in centre ceilings |
| 1/2 in ceiling board (sag-resistant) | Ceilings, especially 24 in centres |
| Moisture / mould resistant | Bathrooms, laundry — not inside a shower |
| Cement board | Tiled wet areas such as shower walls |
Frequently asked questions
How many sheets of drywall do I need for a 12x12 room?
A 12 by 12 foot room with 8 foot walls has 384 square feet of wall; deducting a door and a window leaves about 348, and adding the 144 square foot ceiling gives 492. With 10 percent waste that is 541 square feet, or 17 sheets of 4 by 8 ft, or 12 sheets of 4 by 12 ft.
How much joint compound do I need per sheet?
Budget roughly a gallon of all-purpose compound per 100 square feet of board for taping plus three finish coats, so about one third of a gallon per 4 by 8 sheet. Textured finishes and skim coating use considerably more.
How many screws per sheet of drywall?
About 32 for a 4 by 8 sheet on 16 inch centres — roughly every 12 inches in the field and 8 inches on the edges. At about 320 screws to the pound for 1-1/4 inch screws, that is a tenth of a pound per sheet.
Should I use 4x8 or 4x12 sheets?
Longer sheets mean fewer butt joints, and butt joints are the hardest to hide because there is no tapered edge. But a 4 by 12 sheet of half inch board weighs over 80 pounds and needs two people. Use 12 ft sheets on long open walls and 8 ft sheets in tight or awkward spaces.
How much tape do I need?
About 0.4 linear feet of tape per square foot of board, so a 500 square foot room takes roughly 200 feet. Buy a full 250 or 500 ft roll — tape is cheap and joining two rolls mid-seam is not worth the saving.