Drywall calculator

How drywall sheets are calculated

Drywall is bought by the sheet, so the calculator works out the board area for the walls and the ceiling, adds waste, and rounds each surface up to whole sheets. Everything else on the list is figured from the board you actually buy, because you tape and finish every sheet you hang.

Walls and ceiling are rounded up separately because the sheets run in different directions and leftover wall pieces rarely suit the ceiling. With several rooms, use “+ Add another room”: the wall and ceiling areas of every room are added up first, so each is rounded to whole sheets once for the whole job. Then, from the board ordered (sheets × sheet ft²):

Worked example: 12 × 12 ft room

The calculator opens on a 12 × 12 ft room with 8 ft walls, 1 door and 2 windows, the ceiling included, 4 × 8 ft sheets and 10% waste.

1. Wall area: 2 × (12 + 12) × 8 = 48 × 8 = 384 ft², less 1 × 21 = 21 ft² for doors and 2 × 15 = 30 ft² for windows = 333 ft².
2. Ceiling area: 12 × 12 = 144 ft².
3. Wall sheets: 333 × 1.10 ÷ 32 = 11.45, rounded up to 12.
4. Ceiling sheets: 144 × 1.10 ÷ 32 = 4.95, rounded up to 5.
5. Total: 17 sheets, or 17 × 32 = 544 ft² of board.
6. Screws: 544. Compound: 0.138 × 544 = 75.1 lb, or 2 buckets. Tape: 0.37 × 544 = 201 ft, or 1 roll. Corner bead: 0 outside corners, 0 sticks.

Drywall sheets for common room sizes

Sheet sizes and finishing materials

Longer sheets mean fewer butt joints, which are the hardest seams to finish flat. Pick the longest sheet you can get into the room and carry safely.

Measuring tips and waste

• Measure each wall at the floor, corner to corner, and the ceiling height at a couple of spots. For a second room, a closet or a hallway, use “+ Add another room” with its own height, openings and corners; each room can include or leave out its ceiling.
• Count every door and window, including closet doors. A wide patio door or picture window is roughly two openings; enter it that way.
• Use 10% waste for an ordinary rectangular room. Go to 15% for rooms with many angles, soffits and short walls, or when 54 in sheets have to be cut down.
• For walls over 8 ft, a 4 × 12 sheet hung horizontally or a 54 in sheet on a 9 ft wall avoids a narrow cut strip and the extra seam that comes with it.
• Outside corners are the convex edges: wall returns, soffits, window wraps and the end of a half wall. Each one takes a stick of bead per 10 ft of height.

Hanging order

Hang the ceiling first so the wall sheets hold up its edges, then the top row of each wall tight to the ceiling, then the bottom row with the cut edge at the floor where the baseboard covers it. Stagger the end joints from row to row and keep them off the edges of doors and windows; cutting around an opening instead of jointing at its corner prevents cracks. Twelve-foot and 54 in sheets are heavy, so plan on two people or a drywall lift for ceilings.