Drywall Sheet Calculator
Estimating drywall starts with total wall and ceiling area minus openings, divided by the sheet area, with a waste factor added. This calculator takes room dimensions, wall height, number of doors and windows (with standard opening sizes), and whether you are drywalling the ceiling. Divide total net area by sheet area (4x8 = 32 sq ft or 4x12 = 48 sq ft) and round up to whole sheets. Add a 10 percent waste factor for standard rooms to account for cuts and off-cuts.
Drywall quantity formula
Wall area = 2 x (L + W) x H
Ceiling area = L x W (if included)
Openings = doors x 21 + windows x 15
Net area = Wall area + Ceiling area - Openings
Sheets = ceil(Net area x (1 + waste%) / Sheet area)
Always round up to whole sheets. Partial sheets cannot be returned to the supplier and the cost difference is small compared to running short mid-project.
Drywall installation guidelines
- Hang sheets perpendicular to studs and joists to minimize seams and improve strength.
- Stagger vertical joints between adjacent rows.
- Leave a 1/8-inch gap at floor and ceiling to allow for movement and reduce cracking.
- Use moisture-resistant drywall (green board or cement board) in bathrooms and kitchens.
- 5/8-inch Type X drywall is required for fire-rated wall and ceiling assemblies per IBC.
Drywall sheet calculator: frequently asked questions
How do I calculate drywall sheets for a room?
Calculate the total wall area (perimeter x wall height) plus ceiling area if needed, subtract door and window openings, then divide by the area of one drywall sheet and add 10 percent for waste.
What is the standard drywall sheet size?
The most common size is 4x8 feet (32 sq ft per sheet). 4x12 sheets (48 sq ft) are also popular for reducing seams on tall walls. 4x16 sheets are used by professionals for minimal seams.
How much waste should I add for drywall?
Add 10 percent for simple rectangular rooms. Add 12 to 15 percent for rooms with angled walls, arched openings, or many windows and doors where partial sheets are wasted.
What drywall thickness should I use?
Walls: 1/2-inch is standard for residential walls 16 inches on center. 5/8-inch is required for fire-rated assemblies and for ceilings over long spans. 3/8-inch is used for curved surfaces.
How many screws do I need per sheet of drywall?
Approximately 28 to 32 screws per 4x8 sheet for walls (1 screw every 12 inches on studs). Ceilings require closer spacing. One pound of 1-5/8-inch screws covers approximately 200 square feet.
Official sources
- International Code Council: International Residential Code (IRC) Section R702 Interior Covering.
- Gypsum Association: GA-600 Fire Resistance Design Manual.
Reviewed by the CalculatorHub team, edited by James Graham, 15 June 2026. See our methodology.