Drywall Calculator

Calculate how many sheets of drywall you need for a room, plus screws, joint compound and tape. Supports 4x8, 4x10 and 4x12 sheets with or without the ceiling.

By CalcBuilt Editorial TeamUpdated September 9, 2026Formulas checked against manufacturer specs, see how we calculate.

Quick answer: To find how many sheets of drywall you need, add wall area (perimeter x height minus openings) to ceiling area, divide by the sheet size (32 sq ft for 4 x 8, 48 for 4 x 12) and add 10% for waste. A 12 x 12 ft room with 8 ft walls and a ceiling needs 17 sheets of 4 x 8 drywall.

Results

Drywall sheets to buy: 17 sheets; 4x8 ft sheets, 478 sq ft plus 10% waste
Drywall screws: 526 screws; About 1.8 lb of 1-1/4 in (32 mm) screws
Joint compound: 6 gal; 2 x 4.5 gal (17 L) buckets
Joint tape: 177 ft; 1 x 500 ft (150 m) rolls
Total surface area: 478 sq ft; 334 sq ft walls + 144 sq ft ceiling

Drywall formula

Wall area = 2 x (Length + Width) x Height - openings
Total area = Wall area + Ceiling area (Length x Width)
Sheets = Total area x (1 + waste %) / sheet area  (4x8 = 32, 4x10 = 40, 4x12 = 48 sq ft)

Worked example

A 16 x 20 ft garage with 9 ft walls, one entry door, one 16 x 7 ft overhead door (112 sq ft) and a ceiling: walls 2 x 36 x 9 = 648 sq ft, minus 132 sq ft of doors = 516 sq ft. Ceiling 320 sq ft. Total 836 sq ft, plus 10% = 920 sq ft. That is 29 sheets of 4 x 8 or 20 sheets of 4 x 12.

Quick reference

Drywall sheets for common rooms (8 ft walls, ceiling included, 1 door, 2 windows, 10% waste)
Room size	Total area	4 x 8 sheets	4 x 12 sheets
10 x 10 ft	370 sq ft	13	9
12 x 12 ft	478 sq ft	17	11
12 x 15 ft	562 sq ft	20	13
15 x 20 ft	810 sq ft	28	19
20 x 20 ft	990 sq ft	35	23

How to calculate drywall

Find the total wall area (perimeter times height), subtract door and window openings, and add the ceiling if you are covering it. Divide by the square footage of one sheet (32 for 4x8, 48 for 4x12) and add 10 percent for cuts and mistakes.

A 12 by 12 room with 8 ft walls, one door, two windows and a ceiling has about 478 square feet of surface. With waste that is 17 sheets of 4x8 or 11 sheets of 4x12.

Which sheet size to use

4x12 sheets mean fewer joints to tape and finish, which saves a lot of labor on long walls. They are heavy and awkward in tight spaces, so 4x8 sheets are the practical choice for small rooms, closets and DIY work.

Use 1/2 inch drywall for walls and 5/8 inch for ceilings with 24 inch joist spacing or where fire rating is required. Moisture-resistant board belongs in bathrooms and laundry rooms.

Key facts

A 4 x 8 ft drywall sheet covers 32 sq ft; a 4 x 12 ft sheet covers 48 sq ft.
Plan on about 1 screw per square foot, or 32 screws per 4 x 8 sheet.
One 4.5 gallon bucket of joint compound finishes roughly 350 to 400 sq ft of drywall.
Use 1/2 in drywall on walls and 5/8 in on ceilings and wherever a fire rating is required.

Frequently asked questions

How many sheets of drywall do I need for a 12x12 room?

About 17 sheets of 4x8 drywall for walls and ceiling, or 12 sheets for walls only, including 10% waste.

How many screws per sheet of drywall?

About 32 screws for a 4x8 sheet on 16 inch stud spacing, roughly one screw per square foot. Screws go every 12 inches on walls and every 8 inches on ceilings.

How much joint compound per sheet of drywall?

Roughly 0.4 gallons per 4x8 sheet for three coats. One 4.5 gallon bucket finishes about 10 to 12 sheets.

Sources and references

Next steps for this project

The usual order for a paint & walls project. See all paint & walls calculators.

Results are estimates based on standard formulas and typical product specifications. Confirm quantities with your supplier and local code before ordering.