How to use the drywall calculator
Enter the room's size and wall height, choose whether to include the ceiling and pick the sheet size. Walls and ceiling are counted separately, because ceilings are often hung with longer sheets or ⅝ in board and screwed more closely. The calculator then works out screws at standard spacing, joint tape from the sheet edges, and joint compound from USG's published coverage.
The formulas
walls = 2 × (length + width) × height − large openings
sheets = area × (1 + waste) ÷ sheet area, rounded up
screws per wall sheet = framing members × (sheet height ÷ 16 in + 1)
compound = area × 0.125-0.150 lb per ft²
Worked example: a 14 × 12 ft room, 8 ft walls, with ceiling
- Walls: 2 × (14 + 12) × 8 = 416 ft². With 10%: 457.6 ÷ 32 = 14.3, so 15 sheets.
- Ceiling: 168 ft². With 10%: 184.8 ÷ 32 = 5.8, so 6 sheets.
- Screws: 15 × 28 + 6 × 35 = 630.
- Compound: 584 ft² × 0.125-0.150 = about 73-88 lb.
Sheet sizes and thicknesses
| Use | Typical board |
|---|---|
| Interior walls | ½ in regular |
| Ceilings, especially with joists 24 in on center | ½ in ceiling board or ⅝ in |
| Garage walls next to the house, fire separations | ⅝ in Type X, per code |
| Bathrooms (not inside showers) | Moisture- and mold-resistant board |
| Behind shower tile | Cement board or a waterproof backer, not drywall |
Hanging tips
- Ceilings first, then walls, so wall sheets support the ceiling edges.
- Hang horizontally on walls up to about 8 ft 1 in. Fewer feet of seams, and the seam sits at a comfortable height to tape.
- Stagger butt joints and keep them off the edges of doors and windows, where cracks start.
- Drive screws just below the surface without tearing the paper. A dimpler bit makes it easy.
Common mistakes
- Too little waste on small rooms. Lots of short walls and cutouts mean more offcuts; 15% isn't excessive in a small bathroom.
- Running out of mud. Three coats over tape uses more than people expect. Buy by the pail.
Questions people ask
How many sheets of drywall do I need for a 12x12 room?
With 8 ft ceilings the walls are 384 square feet and the ceiling 144. That's 12 sheets of 4 × 8 for the walls and 5 for the ceiling before waste, about 19 with 10% extra. Doors and windows barely reduce the count, because their cutouts are usually waste anyway.
How many screws per sheet of drywall?
On framing 16 in on center, a 4 × 8 sheet hung on a wall with screws every 16 in takes about 28 screws; on a ceiling, with screws every 12 in, about 35. The Gypsum Association's GA-216 sets the maximum spacing.
How much joint compound do I need?
USG lists 125 to 150 pounds of its all-purpose ready-mix compound per 1,000 square feet of drywall for taping and finishing. A 500 square foot room takes roughly 60 to 75 pounds.
Should I use 4x8 or 4x12 drywall?
Longer sheets mean fewer butt joints to tape, which saves finishing time, but they’re heavy and awkward for one person, and harder to get through doors and up stairs. 4 × 8 is easier to carry and fit through doors.
Do I subtract windows and doors for drywall?
For small openings, no: the cut-out pieces are rarely reusable. Subtract large openings such as patio doors and big windows. This calculator lets you choose.
Sources and assumptions
- USG Sheetrock All Purpose Joint Compound submittal (J1969): approximately 125-150 lb per 1,000 ft² of gypsum panels
- Gypsum Association GA-216 (Application and Finishing of Gypsum Panel Products): screw spacing up to 12 in on ceilings and 16 in on walls
- Tape length is estimated from sheet edges (one long and one short edge per sheet), plus inside corners.
Last reviewed 27 October 2026. Every formula on this page is checked against the worked example above in our automated tests. Found a problem? Tell us.