Drywall Calculator

By HomeAdvisor

Updated January 20, 2021



Wall 1 (in ft.)
Wall 2 (in ft.)
Wall 3 (in ft.)
Wall 4 (in ft.)
Ceiling (in ft.)
*Always purchase a few more sheet than recommended for waste allowance.

On This Page:

  1. How to Estimate Drywall or Sheetrock
    1. Sheets of Drywall in a Bundle
  2. Drywall Layout Calculator
    1. Calculating Angled Walls for Drywall
    2. Types of Drywall Joints
    3. Common Sheetrock or Drywall Measurements
    4. Drywall Coverage by Type
    5. Drywall Ceiling Calculator
    6. How to Calculate Sheetrock Waste
  3. Drywall Mud Calculator
  4. Drywall Estimator Square Footage
  5. FAQs
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How to Estimate Drywall or Sheetrock

You can both estimate the total square feet of drywall, also known as gypsum board, you’ll need and the number of sheets. For an estimate, use the calculator above or follow these steps:

Drywall needed = total area/sheet size.

  1. Multiply the length and height of one wall.
    • Don’t worry about excluding windows and doors, they’ll get trimmed later.
  2. Record the area.
  3. Repeat this process for all walls.
    • Don’t forget to measure each side of a wall that needs covering.
  4. Multiply the length times the width of each ceiling area and combine them.
    • Measure the floor directly below the ceiling area.
  • Add together all wall and ceiling areas.
  • This is the total square feet of your project.
  • Divide this number by the square feet of each drywall sheet
  • Sheet Size Square Feet
    4×8 32
    4×9 36
    4×10 40
    4×12 48
    4×16 64

    1. Round up to the nearest whole number.
    2. For waste, purchase at least two extra sheets. Alternately, you can add 10%.

    How to measure a standard 10 by 15-foot room with 9-foot high ceilings as an example:

    1. Measure the walls: 10 x 9 = 90. For two walls: 180 square feet.
      15 x 9 = 135. For two walls: 270 square feet.
    2. Measure the ceiling: 15 x 10 = 150 square feet.
    3. Add the areas together: 180 + 270 + 150 = 600 total square feet.
    4. Find how many sheets you’ll need using 4×9 sheets: 600 / 36 = 16.67
    5. Round up: 16.67 = 17 sheets.
    6. Add 2 sheets for waste: You’ll need 19 total sheets.

    Sheets of Drywall in a Bundle

    Sheets of drywall come two to a bundle with the smooth, finished side facing inward, towards each other. However, you can purchase odd numbers. Home improvement stores will separate the bundles to meet your needs. It’s usually cheaper to purchase these in bulk.

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    Drywall Layout Calculator

    Before calculating your layout, its best to understand drywall basics. For all 4-foot-wide sheets simply measure the perimeter of the project, divide by 4 and round up to find how many sheets you’ll need. The key to calculate the layout of your drywall is minimizing joints and not worrying about waste. You’ll cut out windows, doors and other openings, so ignore these while calculating.

    1. Decide whether you’ll orient your drywall vertically or horizontally. You’ll determine this by ceiling height:
    • 8-foot or lower: Align 4’x8’ sheets vertically.
    • 9-foot: Use 4’x9’ installed vertically or 4.5’ wide sheets installed horizontally.
    • 10+ foot: Use 4’x10’ or longer sheets installed vertically to match your ceiling height.
    1. Determine ceiling layout by room layout. This will vary by the direction the joists run and the design. Always install ceilings before walls.

    Calculating Angled Walls for Drywall

    Area of a triangle = (Base Length x width) / 2

    To find the area of a wall with an angled top, such as with a vaulted ceiling, just measure the triangular section at the top separate from the rest of the wall. To find the area:

    1. Measure the height of the area.
    2. Measure the length of the area at its base.
    3. Multiply them and divide the result by 2.

    You’ll most likely still use full sheets for the area. When determining how many sheets you need, simply measure the wall at its tallest point and multiply by its length. You can trim the sloping section during installation.

    Types of Drywall Joints

    There are two types of sheetrock joints to understand while calculating your layout:

    • Butt joint are where a long end meets, or butts up against, another. Avoid this by orienting your boards to always have two pieces meet, or join, with the tapered sides. Taping and mudding butt joints always leaves a bulge requiring artistic skill to hide.
    • Tapered joints exist on the long sides of the drywall sheet. The taper starts a couple inches from the edge and thins slightly as it reaches the edge. When placed together, these tapers create a shallow channel for tape and mud without creating a bulge in the wall. Unlike butt joints, it allows fasteners, tape and joint compound to stay flush with the wall.

    Common Sheetrock or Drywall Measurements

    Lumber yards sell gypsum board in predefined sheet sizes: 4 or 4.5 feet wide and 8, 9, 10, 12 or 16 feet long. Understanding the two widths helps you determine layout.

    • 4-foot width: For installing vertically. Each side will always line up with a stud for easy installation and no butt joints. Wall studs, according to building code, are always either 16 inches or 24 inches apart, depending on load. This means there is always one every 4 feet.
    • 4.5-foot width: Install horizontally. Designed for modern, 9-foot-high ceilings. So, a 10-foot-long wall with 9-foot ceilings would need two 4.5×10 foot or longer sheets installed horizontally. That leaves only one seam along the middle.

    Thickness: They come in various thicknesses of 3/8 inch, ½ inch and 5/8 inch. However, thickness has nothing to do with coverage area. Thickness comes into play in a few ways:

    • Thicker pieces provide more sound protection. However, there is a type of specialized drywall with sound dampening materials built in.
    • Building code often requires different sizes. You’ll often use thicker pieces on ceilings for sound and fire resistance.
    • Thinner sheets require fewer fasteners spaced farther apart.

    Drywall Coverage by Type

    The type has little to do with how much coverage you’ll need, except for waste. For example, you may end up with slightly more waste if you have a room that needs three walls covered in ½-inch drywall and one with 5/8-inch Firerock drywall.

    • Fire Resistance: For garages and to separate floors, building code usually requires 5/8-inch fire resistant type.
    • Green board: Another name for moisture resistant varieties used in kitchens, baths, basements and humid environments.

    Drywall Ceiling Calculator

    The amount of gypsum board you’ll need for your ceiling depends on the type you have.

    • Standard flat ceilings. For flat ceilings, its easiest to measure your floor area.
    • Sloped and vaulted ceilings. Measure the length and width up to the peak and multiply to find the area. For a vaulted, do the same for the other side and add the two together.
      • Don’t forget that sloped and vaulted ceilings mean more wall area next to them.

    How to Calculate Sheetrock Waste

    It’s difficult to calculate gypsum board waste because it varies so much from home to home. Waste comes from two main sources:

    • Cutting out the drywall covering doorways, windows, outlets, switches, and light fixture wiring.
    • Incorrect measurements and accidentally breaking a sheet.

    DIYers are more likely to end up with excess waste than those who hire a nearby drywall installer. Best practice is to add 10% to your overall project if you’re new to drywall for a couple reason:

    • Incorrect measurements can ruin a sheet.
    • Before installation, drywall is fragile. Sheet breaks commonly happen and ruin the sheet for use.

    If you’re a pro or a DIYer with some experience, you might want to skip adding a percentage for waste as you may end up with unused sheets. The best ways to reduce waste: hire a pro or calculate exactly how many panels you need.

    You’ll likely end up with far more than 10% waste but that doesn’t mean you want to purchase 10% more sheets.

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    Drywall Mud Calculator

    0.05 lbs. per 1 square foot.

    You’ll need 0.05 lbs. of sheetrock joint compound, also called “mud”, for every square foot of your project. However, you’ll get better results using two different kinds:

    • Taping or all-purpose: Thick and best used for setting tape.
    • Light: Used for the top layers. It’s lighter, goes on thinner and sands off easily for a smoother drywall finish.

    You’ll also need 1 extra gallon for every 50 to 150 square feet of texture. The heavier the texturing, the less space 1-gallon covers.

    How much joint compound per sheet of drywall?

    1.5 to 2 lbs. per 4×8 sheet.

    You’ll need anywhere from 1.5 to 2 pounds of joint compound per 4×8 sheet. It depends on the sheet size, compound type and how much water was used to thin the compound.

    How much drywall mud do I need for texture?

    The amount of joint compound you’ll need for texture depends on the type of drywall texture style, including:

    • Knockdown: 1 gallon per 50 to 75 square feet.
    • Light textures: 1 gallon per 100 to 150 square feet.

    Drywall Estimator Square Footage

    Room Size With 9’ ceilings 4×9 sheets needed
    8’x10’ 404 12
    9’x10’ 432 12
    10’x10’ 460 13
    12’x15’ 486 14
    12’x12’ 576 16
    10’x15’ 600 17
    4.5’x25’ (hallway) 563 16

    The above chart estimates rooms based on modern homes with 9-foot ceilings. Whole home estimates are impossible to determine without knowing the exact dimensions of home’s internal layout.

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    How much drywall do I need for a 2,000-square-foot house?

    It’s impossible to determine how much drywall a 2,000 square foot house needs without knowing the internal layout of the home such as wall height and length, doorways, windows and more. Contact a professional for an estimate.

    How much sheetrock do I need for a 1,200-sq.-ft. house?

    Without knowing the design of the home, how many floors, the floorplan and room height, we can’t determine how much drywall you’ll need. Contact a local professional for an estimate.

    How many drywall screws per sheet?

    Generally, you’ll need a screw every 12 inches for 24-inch stud framing and every 16 inches for 16-inch stud framing. On ceilings, you’ll need a minimum of one screw every 12 inches regardless of joist spacing.

    How many drywall screws or nails you’ll need per sheet depend on the size of the sheet and the spacing of the studs. Screw and nail placements are governed by building codes, which may vary by location.

    How much drywall tape do I need?

    You’ll need enough linear feet of tape to cover every inside corner and joint. Measure all the joints to determine how much you’ll need.

    How much spackle do I need for drywall?

    Drywall spackle isn’t used during drywall installation. It’s a vinyl-based product used to patch and repair holes. Typical drywall repair costs $250 to $800 depending on the type and extent of damage.

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