Drywall Calculator
Calculate drywall sheets for any room from wall dimensions, door and window cutouts, and waste allowance.
Returns sheet count in 4x8 or 4x12 sizes.
Drywall (also called gypsum board or sheetrock) is the standard interior wall and ceiling covering for residential and commercial construction. Estimating the number of sheets correctly prevents multiple trips to the hardware store and minimizes waste from off-cuts.
Basic formula: Total Wall/Ceiling Area = Σ (Width × Height) for each surface Subtract: door openings (typically 3’ × 7’ = 21 ft² each), window openings Add: waste factor (typically 10–15% for a rectangular room; up to 20% for complex shapes) Sheets Needed = Net Area / Sheet Area
What each variable means:
- Sheet Area — standard drywall sheets are 4’ × 8’ = 32 ft² or 4’ × 12’ = 48 ft² (for taller rooms or ceilings to reduce seams)
- Net Area — total surface area after subtracting door and window openings; half-openings (e.g., a window that fills 50% of a stud bay) are still typically counted as full cutouts
- Waste Factor — accounts for cuts around outlets, doors, windows, and angled cuts; 10% is standard for a skilled installer; 15–20% for DIY
Worked example: Room: 12’ × 14’, ceiling height 8’. One standard door (3’ × 7’), two windows (each 3’ × 4’).
Walls:
- Two 12’ walls: 2 × (12 × 8) = 192 ft²
- Two 14’ walls: 2 × (14 × 8) = 224 ft²
- Subtract 1 door: −21 ft²
- Subtract 2 windows: −2 × 12 = −24 ft² Total wall area = 192 + 224 − 21 − 24 = 371 ft²
Ceiling: 12 × 14 = 168 ft² Grand total = 371 + 168 = 539 ft² With 12% waste: 539 × 1.12 = 603.7 ft² Sheets (4×8 = 32 ft²): 603.7 / 32 = 18.87 → 19 sheets (always round up)
Types of drywall:
- Standard (white) — interior walls and ceilings
- Moisture-resistant / green board — bathrooms, kitchens
- Type X (fire-rated) — garages, utility rooms, required between attached garage and living space
- Soundboard — additional layer for noise reduction