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Drywall Calculator

Table of contents

What is drywall (sheetrock)?Types of drywall sheetsDrywall that will save you from fireDrywall sizes and drywall thicknessHow much is a sheet of drywall? – sheetrock prices in USAre you ready for drywalling? – drywall tools and materialsHow much drywall do I need? – required drywall measurementsCalculating the area under sloped walls with drywall estimatorDrywall cost calculator

The drywall calculator, alternatively called the sheetrock calculator, is a handy tool for determining how many drywall sheets you need to cover the walls (and the ceiling) of your room. This drywall estimator can be used together with our paint and wallpaper calculators to finish the interiors of your house. Input your drywall measurements to quickly estimate the number of sheetrock panels you have to buy, and make sure never to overspend on drywall again!

In the text below, we answer the question "what is drywall?" and tell you about the different types of drywall you can find in your home improvement store, as well as what sheetrock prices to expect. Furthermore, you will learn about available drywall sizes and thicknesses. Finally, we will make sure that you won't forget all the necessary drywall tools before you start drywalling.

What is drywall (sheetrock)?

Drywall is a construction material that also has other names: plasterboard, wallboard, gypsum panel, sheetrock, or gypsum board. The current version of gypsum board was developed in the first half of the 20th century. Its popularity rose during World War II, when the cost of building materials was very high, and there was a significant lack of qualified workforce. Fortunately, drywall had a low price and was easy to install, even in a DIY setting.

A drywall sheet is a panel made of gypsum (calcium sulfate dihydrate) compressed between two thick sheets of paper. If we add certain materials to the gypsum mixture, we can improve the drywall resistance against humidity, water, mold, sound, or even fire. Drywall is often used to make interior walls or ceilings, as well as surfacing already existing brick or cement walls.

Drywall is an excellent alternative to plaster because it does not require drying – if you have some experience, you can easily finish drywalling the entire house in just a few days. In fact, it is the current standard to finish homes with drywall. Installation is straightforward: all you have to do is cut it to an appropriate size and then nail or screw it in place. Furthermore, even when it gets damaged or dirty, all you have to do is replace the faulty sheet with a new one. It is as easy as it sounds.

Remember that basic types of drywall are not water-resistant. Do not use them in the kitchen or bathroom, as the moisture will cause them to soften, eventually turning them into a gooey paste. Instead, a water-resistant type of drywall, cement board, or tiles should be used in these rooms.

💡 You might also be interested in our brick calculator and concrete column calculator.

Types of drywall sheets

There are several types of drywall. Their differences come from the additional materials used in their production, which alter their function. Here we present a list of some of the different types of drywall:

  • Regular drywall – This drywall is white and available in many sizes, from relatively thin (1/4" or 6.5 mm) to thick (3/4" or 20 mm). Go to the drywall sizes and drywall thickness paragraph for more details.
  • Greenboard drywall – You can recognize it by its green paper covering. The covering was augmented with water-repellent molecules. This type of drywall costs more but does not soften when exposed to humid conditions. It is a natural choice for rooms with a high moisture level, for example, a kitchen.
  • Blueboard drywall – Similar to greenboard drywall, but it is also resistant to mold, and its covering has a distinguishable blue color. As you may have already guessed, it's more expensive than its green counterpart.
  • Soundproof drywall – Enhanced with sound-absorbing materials such as damping polymers
  • Fire-resistant drywall (type X and C) – Go to the next section: drywall that will save you from fire to see more details.

Aside from the different types of drywall, you can also find some drywall alternatives. In the bathroom, you could use tiles and cement board. Cement board is made of cement and reinforcing fibers. It comes in sheets similar in shape and thickness to drywall sheets and may be laid by itself or as the basis for tiles. Learn more about tiling with our tile calculator.

Drywall that will save you from fire

If we check the chemical formula of gypsum, the compound that forms the core of a drywall sheet, we will see that it contains a high percentage of water: Ca2SO42H2O\rm Ca_2SO_4 \cdot 2 H_2O. That's quite surprising, isn't it? When the drywall is exposed to fire, the water in gypsum becomes free and evaporates. What remains is the calcium sulfate: Ca2SO4\rm Ca_2SO_4. This process is called calcination, and it requires vast amounts of energy. This energy cost means that it takes some time for the fire to break through the drywall layer.

Based on this effect, you can see that drywall is fairly fire-resistant by itself. But some methods can enhance its fire-holding abilities even more. Apart from laying multiple layers of drywall sheets or using thicker drywall, you can buy special fire-resistant drywall.

Type X drywall contains glass fibers that prevent the drywall from cracking as the water inside evaporates. Type C is enhanced with the same glass fibers as type X but also contains vermiculite. This substance expands (increasing its volume while decreasing its density) when exposed to high temperatures, so it fills in any emerging cracks in the drywall.

It is worth considering drywalling the wall separating your house and garage with fire-resistant drywall. It is a good investment in the safety of your family.

Drywall sizes and drywall thickness

The most common drywall sizes in the US are:

  • 4’ x 8’
  • 4’ x 9’
  • 4’ x 10’
  • 4’ x 12’

In other countries, we can find drywall in metric units:

  • 1200 x 600 mm
  • 1200 x 2000 mm
  • 1200 x 2600 mm
  • 1200 x 3000 mm

You will finish your project quicker if you use a bigger drywall size as one sheet will cover more square footage. However, large sheetrock sheets are also more challenging to handle because of their increased weight and low maneuverability. Smaller drywall sizes are more comfortable to operate on, and you should choose for drywalling small rooms and areas.

There are several drywall thicknesses available. 1/4” and 3/8” (6.5 mm) thick panels are suitable for renovating ceilings and curved areas. 1/2” (12.5 mm) thick sheetrock sheets are the most common and are a perfect choice for standard walls. You should use thicker drywall sheets (more than 5/8” or 15 mm) on walls that you want to be sound (or fire) proof.

How much is a sheet of drywall? – sheetrock prices in US

Sheetrock prices typically range from $6 to $15 and depend on their size:

  • 4’ x 8’ drywall sheets – $6-$8
  • 4’ x 9’ drywall sheets – $9-$11
  • 4’ x 10’ drywall sheets – $10-$12
  • 4’ x 12’ drywall sheets – $10-$14

Naturally, if you want to use a thicker drywall sheet, you will also have to pay more. Special usage sheetrock prices are also higher; there is a price to pay for enhanced durability or resilience from water, noise, or fire.

Are you ready for drywalling? – drywall tools and materials

Here, we provide you with a list of the necessary drywall tools and materials to make sure that you have not forgotten anything:

  • Drywall mud — Common name for the joint compound. With drywall mud, you will be able to join sheets of drywall and cover any holes. It comes in different volumes and three versions: dry, premixed, and low-dust. A dry joint compound is cheaper than its premixed counterpart, but you have to mix it with water by yourself. Be careful! It is not easy to add the correct amount of water to preserve the right ratio. If you don't want to vacuum your house after drywalling, low-dust drywall mud is the choice for you.

  • Drywall tape — Although typically made of paper, it holds two sheets of drywall together firmly. Drywall tape has to be soaked first in drywall mud. After that, you can put it on a joint between drywall sheets and let it dry. Another, more expensive version of drywall tape is fiberglass tape. This tape is more durable and easier to apply as it is self-adhesive.

  • Drywall corner bead — Serves to join drywall sheets at the corners of walls. These areas are easily damaged during moving of furniture or even routine daily activities. Drywall corner beads are made of plastic or metal and can support many strikes.

  • Drywall screws — Used to fix drywall sheets to walls or other firm objects. Nowadays, drywall screws have surpassed drywall nails as they don't pop out.

  • Drywall T-Square — Essential drywall tool. Only by using a drywall T-square can you be sure that your drywall panels are correctly in place.

  • Drywall saw — Used to cut drywall sheets so they can fit into more irregular spaces. It is more comfortable to use an electric drywall saw, but a manual one will do the job as well.

  • Cordless drill or drywall screw gun — To effectively load up or screw-in drywall screws

  • Drywall knife — Used for slopping mud, tapping, and feathering. A smaller drywall knife will be better at slopping and tapping, while a larger drywall knife will be more efficient at feathering and making final corrections.

  • Sanding pole or sponge — For final sanding and smoothing. With a sanding pole, you can easily reach higher places.

How much drywall do I need? – required drywall measurements

If you want our drywall estimator to calculate the number of panels you need, you will have to provide it with some data regarding your room. Make sure to input the following drywall measurements:

  • Room dimensions — You need to type in the length, width, and height of your room.

  • Ceiling — Choose whether you want to include the ceiling in your calculations.

  • Room surface area — This value will be calculated automatically. Still, if your room has a different shape than a rectangular cuboid, you can also input the surface area directly into our drywall calculator. To calculate the area of some unusual shapes, search Omni for the shape plus "area". Maybe one of your walls is a trapezoid? Oh, and don't forget to check our circumference and circle calculators for some extravagant projects!

  • Doors — You can use the default dimensions or type in custom ones. Once you type in the number of doors in the room, the drywall estimator will find their total area automatically.

  • Windows — Again, you can leave the default dimensions of windows or customize them. If your windows vary in size, you can also calculate the total area manually.

  • Drywall panel type — Choose the size of the drywall panels you will buy. Our drywall calculator lists the most common sizes in the USA and other countries. You may read more about the different drywall sizes in the drywall sizes and drywall thickness section.

Once you have decided on all of the values listed above, the sheetrock estimator will automatically display the number of drywall panels that you need. Remember to buy a bit more (ideally, 10% more) to account for all cut-outs, waste, and replacement (to see why, go back to the what is drywall (sheetrock)? section).

Calculating the area under sloped walls with drywall estimator

With our drywall calculator, you can also incorporate the area of any spaces under sloped walls into the total room surface area calculation. How to do it?

  • Firstly, determine whether your room has sloped walls. Sloped walls exist in rooms directly under the roof where there is no attic. Although sloped walls have a rectangular shape by themselves, they also limit the room's other walls by creating a triangle-like shape on top of them. It may look like this:
image of two exemplary walls limited by sloped walls
  • Secondly, measure the height and the base of the triangular space as shown in the picture. Height is marked with h, and the base is labeled with b.

  • Now, we can perform our calculations. To get the area of this space, we need to use the equation for the area of a triangle:

    area = height × base / 2

  • Finally, if there are some more identical triangular spaces in the room, multiply the estimated area of one triangular space by the number of all triangular spaces.

  • Watch out! If your room has sloped walls, you should measure the height of your room only to the base of the triangular space under the sloped wall (not to the top of the ceiling).

Remember that there is no need to do all the calculations by hand. Our sheetrock calculator can do it all for you.

Drywall cost calculator

You can also use the drywall cost calculator to determine the total cost of all the required panels. Simply input the unit price in the Cost per panel field (in the USA, it is typically $6 to $15 per panel, depending on its dimensions, see the how much is a sheet of drywall? – sheetrock prices in US section). The drywall cost calculator will display the total drywall cost for you.

Room dimensions

Room surface area

Drywall amount

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