1. Measure your walls
Record the height and width of each wall. For a full room, measure the perimeter and multiply by ceiling height to get total wall area.
What is drywall square footage?
Drywall square footage is the total wall surface area that needs to be covered with drywall sheets, measured in square feet. To calculate drywall square footage, multiply wall height by wall width, then subtract the area of all windows, doors, and other openings. A standard 4×8 drywall sheet covers 32 square feet. Knowing total wall area helps you order the correct number of sheets and avoid costly material shortages or overages.
Getting started
How to Calculate Drywall Square Footage
To calculate drywall square footage, measure each wall's height and width, multiply to get wall area, subtract window and door openings, then divide by the sheet size (typically 32 sq ft for a 4×8 sheet). Add 10-15% for waste from cuts and fitting around corners.
2. Subtract openings
Measure each window and door opening. Use the Wall with Window shape to automatically subtract these areas from the total wall surface.
3. Get sheet count and cost
The calculator shows net wall area in square feet. Divide by 32 for standard 4×8 sheets. Add a price per sheet or per square foot to estimate total material cost.
Quick reference
Reference
1 acre = 43,560 square feet
1 square yard = 9 square feet
1 square meter = 10.764 square feet
1 square inch = 0.00064516 square feet
Core formula
Basic Formula for Area
Area is the amount of space occupied by a 2-dimensional shape. The shape could be a floor, a wall, a playground, or a field. The simplest formula for area applies to any rectangular shape:
Area = Length × Width
Measure the length and width of the space in feet. Multiply the two values to get the area in square feet. A rectangular room that is 12 feet (3.66 meters) long and 10 feet (3.05 meters) wide has an area of 120 sq ft (11.15 sq m).
Square yardage is area measured in yards, and square meters is area measured in meters. Measure in feet, find the area in square feet, then convert to the unit you need.
For an L-shape room, split the floor into 2 rectangular sections, calculate each area, and add the results. Convert all measurements to the same unit before multiplying, if your dimensions are in different units like inches and feet.
Shape formulas
Calculating Square Footage for Walls
The Drywall Calculator uses wall-specific formulas to calculate net drywall area after subtracting openings.
Wall with Window Shape
Calculate drywall area with window cutout
Using measurements in feet: Net Area (ft²) = (Wall Height × Wall Width) - (Window Height × Window Width). Measure the full wall first, then subtract each opening. A wall 12 ft wide and 8 ft tall with a 3 ft × 4 ft window has a net drywall area of 96 - 12 = 84 sq ft.
Waste factor
Adding 10% Surplus for Materials
Add a 10% surplus to your calculated area to account for material waste during cutting, breakage, and pattern matching. This waste factor applies to flooring, carpet, tiling projects, and landscaping materials.
Original Area100 sq ft
+10%
Order Amount110 sq ft
Total Material = Area × 1.10
A room with 200 sq ft of floor area needs 220 sq ft of material: 200 × 1.10 = 220 sq ft. Increase the surplus to 15% (multiply by 1.15) for diagonal flooring installation patterns or complex tiling projects with many cuts. The Square Foot Calculator includes a waste factor field for this calculation.
FAQ
Frequently Asked Questions
How many sheets of drywall do I need?
Calculate total wall area in square feet, subtract window and door openings, then divide by the sheet size. A standard 4×8 sheet covers 32 sq ft. For a room with 480 sq ft of wall area minus 60 sq ft of openings, you need 420 ÷ 32 = about 14 sheets, plus 10% for waste.
How do I calculate drywall for a room?
Measure the perimeter of the room and multiply by the ceiling height to get total wall area. Subtract the area of all windows and doors. A 12×14 room with 8-ft ceilings has a perimeter of 52 ft and a total wall area of 416 sq ft before subtracting openings.
What size is a standard drywall sheet?
The most common drywall sheet is 4 feet × 8 feet (32 sq ft). Other sizes include 4×10 (40 sq ft), 4×12 (48 sq ft), and 4×14 (56 sq ft). Longer sheets reduce the number of seams on taller walls.
Do I subtract windows and doors from drywall calculations?
Yes, subtract the area of windows and doors from total wall area before calculating sheet count. A standard door opening is about 21 sq ft (3 ft × 7 ft) and a typical window is about 12 sq ft (3 ft × 4 ft).
How much extra drywall should I buy for waste?
Add 10% to 15% extra for waste, cuts, and mistakes. For rooms with many openings or corners, use 15%. For simple rectangular walls, 10% is usually sufficient.
How much does drywall cost per square foot?
Standard 1/2-inch drywall costs about $0.40 to $0.65 per square foot for materials only. Installation labor adds $1.00 to $2.50 per square foot depending on complexity. Enter your price per square foot in the calculator to estimate total cost.