When finishing or remodeling the interior walls of your home, one of the most common building materials used is drywall. Also known as wallboard, sheetrock or gypsum board, drywall comes in large sheets that are installed on the wall studs or ceiling joists and then mudded and taped to create a seamless surface ready for priming and painting.
If you are installing drywall yourself, one of the first calculations you need to make is how many sheets of drywall you will need to purchase to cover the wall or ceiling area you are working on. This involves measuring the square footage of the area and determining how many full sheets and partial sheets are needed to cover that space.
Estimating Square Footage
The first step in figuring out drywall needs is calculating the total square footage of wall space to be covered. Here are some guidelines for measuring square footage:
- Measure the length and height of each wall section and multiply them together to get the square footage of that section.
- Add up the square footages of all wall sections being covered with drywall.
- For sloped ceilings, measure the slope at its longest and shortest points and calculate the average.
- Remember to calculate both sides of any interior walls being covered.
- Round up to the nearest whole foot after calculating total square footage.
Let’s assume for this exercise that the total wall space to be drywalled is 600 square feet. This will be the basis for the drywall calculations below.
Drywall Sheet Dimensions
Drywall sheets come in standard sizes:
- 4 x 8 feet sheets are the most common
- 4 x 10 feet sheets are also used frequently
- 4 x 12 feet sheets are available but less common
Drywall thickness can be either 1/2 inch or 5/8 inch. The thicker 5/8 inch sheets are recommended for ceilings to prevent sagging.
For our 600 square foot example, let’s assume the drywall sheets to be used are the typical 4 x 8 feet size in 1/2 inch thickness.
Coverage of Full Sheets
A 4 x 8 feet sheet of drywall covers 32 square feet of wall space (4 feet wide x 8 feet tall).
To determine how many full sheets are needed, take the total square footage to be covered and divide by 32.
For our example:
Total square footage: 600 sq ft
Square footage per sheet: 32 sq ft
600 sq ft / 32 sq ft per sheet = 18.75 sheets
Rounding up, you would need 19 full sheets of 4 x 8 feet drywall to cover the 600 square feet in this example.
Accounting for Partial Sheets
The full sheets calculated above will cover 608 square feet (19 sheets x 32 sq ft per sheet). That leaves an extra 8 square feet needed to reach the total 600 square feet of our example project.
To finish covering the wall space, you will need to cut partial sheets of drywall. Leftover scraps from cutting full sheets to fit can often be used productively for this purpose.
If no scraps are available, divide the leftover square footage needed by the width of the drywall to determine how much extra drywall length is required.
For our example:
Leftover square footage needed: 8 sq ft
Sheet width: 4 ft
8 sq ft / 4 ft = 2 feet
So you would need 2 linear feet of drywall from a partial sheet to complete the 600 sq ft project area.
Drywall Estimating Formula
The calculations above can be summarized in a basic formula to estimate drywall needs:
Total sheets = (Total square footage / Sheet coverage) + Partial sheets
Sheet coverage is 32 sq ft for 4×8 sheets or 40 sq ft for 4×10 sheets.
For our 4×8 sheet example:
Total sheets = (600 sq ft / 32 sq ft per sheet) + Partial sheets
= 19 full sheets + Partial sheets
Ordering Drywall
When purchasing drywall for a project, it’s a good idea to add 10-15% extra to account for damaged sheets, off-cuts and mistakes.
For our example, with 19 full sheets estimated, adding 15% extra would mean ordering:
19 sheets x 1.15 = 21.85 sheets
Rounding up, you would want to purchase 22 sheets total of 4×8 feet drywall.
In addition to the full sheets, purchase enough drywall to cover the estimated partial sheet footage, which is 2 linear feet in our example.
If buying full sheets, you may want to purchase a few extra sheets for scrap material. For a 600 sq ft project, an extra 2-3 sheets should provide plenty of scrap for cutting partial pieces.
Cutting Drywall
When working with full 4×8 or 4×10 sheets of drywall, you will need to cut them to fit your wall dimensions. Here are some tips for measuring and cutting drywall:
- Use a drywall T-square or rectangular piece of wood to mark cutting lines.
- Cut sheets with a utility knife scored several times over the cutting line.
- Snap sheet backwards to break along cut line.
- For openings like windows, measure and mark opening size plus 2 inches overlap on all sides.
- Cut out opening with utility knife or drywall saw.
- Use drywall saw for curved cuts.
Measure carefully and use scraps wherever possible to reduce waste. Plan your layout to make best use of full sheets and minimize partial sheets needed.
Drywall Primer
Once the drywall sheets are installed on your walls and ceilings, the seams and screw holes will be concealed with joint compound and drywall tape. After sanding smooth, the drywall will be ready for priming and painting.
Drywall primer serves an important purpose. It seals the porous gypsum core and creates a uniform surface for painting. Priming makes the paint color look even and consistent.
Use high quality drywall primer designed for new drywall. The primer can be either tinted or untinted based on whether you want to help pre-tone the wall color. Apply primer over all drywall surfaces with a paint roller according to manufacturer’s instructions.
Priming drywall before painting will lead to a much more attractive and durable finish coat.
Drywall Paint
Once primed, the drywall is ready for painting with a high quality interior latex or enamel paint. Consider a paint formula designed specifically for new drywall for best results. If using a general purpose interior paint, look for qualities like:
- 100% acrylic or latex formula
- Matte, eggshell, or satin finish
- Mold and mildew resistant
- Great hide and coverage
Flat paints are not ideal for walls as they tend to scuff and stain easily. An eggshell or satin sheen will provide some durability and be easy to clean. Apply two coats of paint for best coverage and uniformity of appearance.
Be sure to use high quality applicator tools – a combination of brush for cutting-in edges and paint roller for large areas. Follow the manufacturer’s recommended drying time between coats.
Conclusion
When installing 600 square feet of drywall as outlined in this example, you would need:
- 22 sheets of 4 x 8 feet drywall
- Partial sheet piece or scrap to cover 8 sq ft
- Drywall joint compound, tape, tools
- Drywall primer
- Interior paint and supplies
Carefully measuring the space, calculating required sheets, cutting to fit, priming and painting will result in an attractive new drywall installation that revitalizes your interior rooms and walls.