Drywall (also commonly referred to as "gypsum board") is a modern adaptation of the traditional plaster wall finish that has been used for over a century in most types of construction. Available in several sizes, thicknesses and fireproofing, drywall has become a vital material in most types of construction ranging anywhere from commercial to residential. The installation of drywall begins with the process of material and cost estimation, and through a generally straightforward process, can usually be successfully completed by just about anyone with a basic knowledge of math and construction practice.
Things You'll Need
 Tape measure
 Calculator

Measure both the length and height of a wall (in feet), using the tape measure; round the length measurement to the next higher whole foot to make later calculations simpler.

Multiply the measurements made in step 1 to find the total surface area of the wall in square feet. Disregard any openings in the wall (doors and windows); while these openings will not be covered with drywall, not subtracting their surface area will result in extra material, which will help account for any wasted material during the drywall installation process.

Repeat steps 1 and 2 on all other walls to be covered with drywall, and add the surface area of each to find the total surface area of the drywall project.

Multiply the area calculation from step 3 by 1.1; this will add an extra 10% of square footage, which will account for any wasted material during installation.

Call a local drywall or building materials supplier and quote the current unit cost of drywall; this cost is usually based on a persheet basis, and the final cost may depend on what size sheet you use (4 by 8, 4 by 10, or 4 by 12foot sheets).

Divide the total square foot calculation of the drywall project (from step 4) by the total surface area of the sheet size you will be using (example: 4 by 8foot sheets have a surface area of 32square feet) to find the total number of drywall sheets are needed; round any measurement to the next higher whole number, as partial sheets of drywall are not available.

Multiply the unit cost per sheet (found in step 5) by the total number of needed sheets of drywall (found in step 6) to find the total cost of drywall sheets for the project.
Tips & Warnings
 The amount and cost of drywall fasteners (nails or screws) depends on wall stud spacing (16 or 24inches oncenter), and may differ depending on drywall thickness and fastener type; consult with a drywall expert or local building codes for fastening requirements and amounts.
 Estimating labor for drywall installation varies between contractors, and is either estimated on an hourly basis or flatrate (cost per square foot). Both of these methods of estimating labor require prior drywall installation experience, as they are usually based on an existing knowledge of how much time it personally takes to fully install drywall for a given project.
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References
 “Estimating in Building Construction (6th Edition)”; Frank R. Dagostino and Leslie Feigenbaum; 2002
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