Many home repairs may call for putting up new drywall. Typically, these sheets come in standard 4-by-8-foot sizes, so most often it's not too tough to estimate how much you'll need for a given job. Figuring out before the job begins how much joint compound you'll need is almost as easy and can save you return trips to the store to replenish materials.
Measure the area where the new drywall will be installed. To get the square feet of the area, measure the width and height and multiply the two numbers. A standard 4-by-8 sheet, for example, measures 32 square feet.
Calculate that one gallon of joint compound will be needed to mud between 100 and 200 square feet of drywall.
Realize that a number of factors may affect how much joint compound you will need. If it's applied thicker than necessary or needs several applications, a gallon's coverage will be much closer to 100 square feet than 200. Also, if many smaller pieces of drywall are pieced together to cover an area, more seams will mean more joint compound must be applied.