How to Calculate for Drywalling a Basement

Measure the length and height in feet of the basement walls, and the length and width of the ceiling with a tape measure. If the walls have odd angles, measure these portions separately from the main walls. The object is to get the most precise measurement so you do not buy more drywall than you need.

Multiple the length and height of each wall, including any of the odd-shaped portions, and the length and width of the ceiling. This is the square footage for each wall and the ceiling. Add all of the square footages together. This is the total square footage.

Measure any doorways and window openings in feet. Multiple each of their heights and lengths. Add all of the doorway and window measures together. This is the square footage of drywall that you do not need to buy. Subtract this amount from the total square footage amount in Step 2.

Divide the final amount in Step 3 by 32 since each drywall piece is typically 4-by-8 feet. The result is the number of 4-by-8 feet drywall sheets you will need. Add another 20 percent to the amount for mistakes.