Drywall Calculator

How to use the drywall calculator

1. Pick what you are covering: walls and ceiling, walls only, the ceiling only, or one wall.
2. Type the room’s length and width and the ceiling height (12′ or 3.66 m both work), and the number of doors and windows.
3. Open Sheets, studs and window size to choose the sheet length yourself, say whether your studs are 16″ or 24″ apart, and give your window size.
4. You get the sheets to buy, how they hang, every sheet drawn on the walls, and the tape, joint compound and screws. Copy link keeps the result.

Drywall for common room sizes

One 36 × 80″ door and one 36 × 48″ window each, studs 16″ apart. The sheet length is the one with the fewest end joints, then the fewest sheets.

Drywall sheet sizes, weights and screws per sheet

USG’s Sheetrock UltraLight ½″ panels come 4 ft or 54″ wide and 8 to 16 ft long, at about 1.25 lb a square foot; the screws are the Gypsum Construction Handbook’s 1,000 per 1,000 sq ft on framing 16″ apart and 850 on 24″, spread over one sheet.

The rules behind the count

Which way the sheets hang

The Gypsum Construction Handbook (USG) prefers sheets hung across the framing: it cuts the joint to finish by up to 25%, and the long seam lands at a comfortable height. On walls up to 8′ 1″ high, 4 ft sheets go across in two rows. From 8′ 1″ to 9′ 1″, 54″ sheets across still need only two rows. Taller walls, and walls 4 ft wide or less, get sheets hung upright, one piece floor to ceiling. On a ceiling, the sheets run whichever way leaves fewer joints.

Which sheet length

A sheet’s long edges are tapered (USG) to take the tape and compound; its ends are not, so an end joint, where two ends meet, is the hardest seam to hide. So the calculator tries 8, 10 and 12 ft sheets and picks the one with the fewest end joints, then the fewest sheets. An offcut is used again along the next wall or row, never bent around a corner.

Doors, windows and the finishing materials

Estimators count doors and windows as wall for the sheets (“figured solid”, in the handbook’s words): their offcuts rarely fit anywhere else. They come out of the area you finish. Per 1,000 sq ft of drywall, the handbook gives about 370 ft of paper tape and 138 lb of all-purpose ready-mixed compound; USG’s All Purpose joint compound says about 10 gallons for the same area, in 4.5 gallon pails.

Worked examples

A 12 × 10 ft room with a 9 ft ceiling. 54″ sheets hung across cover the walls in two rows: 11 sheets of 54″ × 12 ft, each about 68 lb, and still no end joints.

The same room with a 10 ft ceiling. Too tall for two rows across, so the sheets hang upright: 15 sheets of 4 × 10 ft, 12 on the walls and 3 on the ceiling.

One 12 ft wall, 8 ft high, no openings. 2 sheets of 4 × 12 ft, one row above the other, 96 sq ft to finish: about 36 ft of tape, 1 gallon of compound and 100 screws.

Common drywall mistakes

• Buying 4 × 8s for everything. In a 12 × 10 room they take 15 sheets and leave 11 end joints; 4 × 12s take 11 and leave none.
• Hanging upright on an 8 ft wall. Every seam then runs floor to ceiling, and there is more of it to finish.
• A third row on a 9 ft wall. Two rows of 54″ sheets cover it with one seam.
• Carrying a 4 × 12 alone. At about 60 lb even the lightweight sheet is heavy to lift over your head: plan the ceiling with a helper.
• Running out of compound. Three coats on every joint, screw and corner add up: about 10 gallons per 1,000 sq ft.

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