About the Drywall Calculator
This drywall calculator estimates how many sheets of drywall (sheetrock or plasterboard) a room needs. Enter the room length, width and wall height, choose whether to include the ceiling, and subtract doors and windows. It returns the net area, the number of sheets for your chosen size with a waste allowance, and a materials list of screws, joint tape and joint compound.
It is aimed at DIYers finishing a basement, remodeling a room or framing an addition, and at contractors doing a quick takeoff. Larger 4 × 10 or 4 × 12 ft sheets mean fewer seams to tape but are heavier to hang.
Openings are deducted as a standard 3 × 7 ft door (21 sq ft) and 3 × 5 ft window (15 sq ft). Screw, tape and compound quantities are common rule-of-thumb figures — about one screw per square foot of board, 370 ft of tape and 138 lb of ready-mixed compound per 1,000 sq ft — and real usage varies with finish level.
With the default inputs, the drywall sheets is 17. Change any value above to recalculate instantly.
How to use the drywall calculator
- 1Measure the room length, width and wall height in feet.
- 2Turn on the ceiling if you are hanging it too.
- 3Enter the number of doors and windows to deduct.
- 4Choose the sheet size and a waste allowance (10% for simple rooms, 15% for many cuts).
- 5Read the sheet count and materials list, then add a spare sheet for damage.
Formula and method
Wall area is the room perimeter, 2 × (length + width), multiplied by the wall height. Door and window openings are subtracted using standard sizes, and the ceiling (length × width) is added if selected. The net area is increased by the waste allowance and divided by the area of one sheet, then rounded up to whole sheets.
Accessories use common takeoff ratios based on net area: roughly 1 screw per square foot of board hung (about 32 per 4 × 8 sheet), 0.37 ft of paper tape per square foot, and 0.138 lb of ready-mixed joint compound per square foot for a standard three-coat finish.
- L, W, H
- Room length, width and wall height (ft)
- waste
- Waste allowance as a decimal (10% = 0.10)
- ⌈ ⌉
- Round up to a whole sheet
Worked examples
12 × 12 ft bedroom with ceiling
The walls are 2 × (12 + 12) × 8 = 384 sq ft and the ceiling adds 144. Subtracting one door (21) and two windows (30) leaves 477 sq ft. With 10% waste that is 524.7 sq ft ÷ 32 = 16.4, so you need 17 sheets of 4 × 8 drywall.
10 × 12 ft room, 9 ft walls, 4 × 12 sheets, no ceiling
Walls are 2 × 22 × 9 = 396 sq ft, minus a door and window (36) = 360 sq ft. Adding 10% gives 396 sq ft ÷ 48 = 8.25, so buy 9 sheets of 4 × 12.
20 × 15 ft basement, walls only, 15% waste
The walls total 2 × 35 × 8 = 560 sq ft. Two doors (42) and four windows (60) leave 458 sq ft. With 15% waste that is 526.7 sq ft, or 17 sheets of 4 × 8.
Frequently asked questions
How many sheets of drywall do I need for a 12 × 12 room?+
With 8 ft walls, a 12 × 12 room has 384 sq ft of wall and 144 sq ft of ceiling. After typical door and window deductions and 10% waste, that is about 17 sheets of 4 × 8 drywall, or 12 without the ceiling.
What size drywall should I buy?+
4 × 8 ft sheets are easiest to carry and fit most cars. 4 × 10 and 4 × 12 ft sheets cover more with fewer seams, which saves taping time, but usually need two people to hang.
What thickness of drywall is standard?+
Half-inch drywall is standard for walls in most homes. 5/8-inch Type X is used where a fire-resistance rating is required — for example the garage ceiling under a bedroom or other habitable room — and is also common on ceilings with 24-inch framing because it resists sagging.
How many screws per sheet of drywall?+
A 4 × 8 sheet typically takes about 28–32 screws, spaced roughly 12 inches apart on ceilings and 16 inches on walls. Follow the manufacturer’s schedule and local code for exact spacing.
How much joint compound do I need?+
A common estimate is about 138 lb of ready-mixed compound per 1,000 sq ft of drywall for a three-coat finish — a little over two 4.5-gallon buckets, which weigh about 62 lb each. A higher level of finish uses more.