Texture Determines Amounts
Drywall mud can be used in different types of texturing, and the type of texturing you want determines the amount of mud you need. Using a texturing gun, for instance, to spray a thin coating of mud onto the wall requires less mud than using a putty knife to apply strokes of mud by hand. Before attempting to make up your mud, you should decide on the texture you want to use on the wall.
With a spray gun, you can create texture in a variety of sizes on a wall, ranging from small to large dots. This is commonly referred to as “orange peel” texture. With a putty knife -- and sometimes with a spray gun as well -- you can apply less uniform texturing by spreading mud over the surface in random strokes. This is called “knockdown” texture. Larger textures such as knockdown generally require more thin mud than smaller textures such as orange peel.
Mud that has not been mixed generally comes in a box, but you can purchase ready-to-use drywall mud that's already been thinned with water. If you mix your own mud, place the entire package of mud into a 10-gallon bucket and add 1 cup of water at a time, stirring with a mixing tool on a drill. Mix only one batch of mud at a time and note the amount of water added to the mud.
How Much Mud
Begin every drywall texturing project with one batch of mud, which provides sufficient coverage for most rooms and styles of texturing. The thinner you mix the mud, the less mud you generally need. Start using the mud to texture one wall of the room, then move onto an adjacent wall. Texturing at different times won’t hurt your texture job, so if you run out of mud, you can get more and finish where you leave off.