Drywall Calculator
Sheets of drywall for a room in 4×8, 4×10 or 4×12, with the ceiling and the openings, and the compound, tape and screws to finish it.
4x8 sheets
21
584 ft² of board · 584 screws
- Wall area
- 416 ft²
- Ceiling area
- 168 ft²
- Board areawalls and ceiling, less openings
- 584 ft²
- Sheets 4x8
- 21
- Joint compoundready-mixed, about 1 gal per 100 ft²
- 5.8 gal (2 × 4.5 gal)
- Tapeabout 370 ft per 1,000 ft²
- 216 ft (1 × 250 ft)
- Screwsabout one per square foot, framing 16" on centre
- 584
Kalku is coming to iPhone and Android
The app has a Drywall shortcut on its keypad that works from the room's length, width and height registers, and calcs for studs, sheathing, insulation, trim, paint and flooring alongside. Every room is drawn in 3D and can be saved and shared as a PDF for the supplier. Works with no signal.
How it is worked out
The walls of a rectangular room are its perimeter times the ceiling height: 2 × (length + width) × height. Add the ceiling (length × width) if you are boarding it, subtract the doors and windows you want to leave out, and you have the board area. Add the waste allowance, divide by the area of one sheet and round up.
Finishing materials scale with the board area too, and the calculator uses the figures USG publishes for estimating, as the Kalku app does: about a gallon of ready-mixed joint compound per 100 square feet, 370 feet of paper tape per 1,000 square feet, and roughly one screw per square foot with framing at 16 inches on centre.
Worked example: a 14 × 12 ft room with 8 ft walls
The job the calculator opens with, ceiling included, in 4×8 sheets with 10% for waste:
- Walls: 2 × (14 + 12) × 8 = 416 ft². Ceiling: 14 × 12 = 168 ft². Board area: 584 ft².
- Sheets: 584 × 1.1 = 642.4 ft² ÷ 32 ft² = 20.1, so 21 sheets.
- Compound: 584 ÷ 100 = 5.8 gallons, two 4.5 gallon pails.
- Tape: 584 × 0.37 = 216 ft, one 250 ft roll. Screws: about 584.
Rooms that are not rectangles
Break an L-shaped room into two rectangles and run each one, leaving out the shared wall the second time. A sloped ceiling covers more board than its floor plan: its real area is the plan area × the slope factor of its pitch (the roof pitch calculator gives it), so leave the ceiling out here and add those sheets on their own. A gable wall is a triangle: half its width × its rise.
Questions
How many sheets of drywall do I need for a 12 × 12 room?
With 8 foot walls and the ceiling, the board area is 4 walls × 12 ft × 8 ft = 384 ft² plus a 144 ft² ceiling: 528 ft². With 10% for waste that is 19 sheets of 4×8, or 13 sheets of 4×12. Leave the ceiling out and it is 384 ft²: 14 sheets of 4×8.
Should I deduct doors and windows?
The calculator lets you, by their area together. Many people deduct only large openings, such as a patio door or a wide window, and leave small ones in to cover the offcuts and breakage. Either way, the waste allowance is there for the cuts around them.
How much joint compound and tape will I need?
The calculator uses USG's estimating figures: about 1 gallon of ready-mixed compound per 100 square feet of board, 370 feet of tape per 1,000 square feet, and about one screw per square foot with framing 16 inches on centre. Compound is shown in 4.5 gallon pails and tape in 250 foot rolls. Textured finishes and extra coats take more.
Which sheet size should I use?
Longer sheets mean fewer joints to tape, which saves finishing time: a 12 foot wall can be one 4×12 sheet across instead of a 4×8 and an offcut. They are heavier and harder to get into a room, though, and 4×8 is the one every store has. Try each size in the calculator and compare the counts.
