Drywall Calculator — Sheets Needed for Walls or Ceilings
Drywall (plasterboard) comes in standard sheet sizes. Getting the count right before your delivery avoids costly re-orders and delays. Enter your total area and sheet dimensions to find out exactly how many boards you need.
How we calculate
Sheet area = width × height. Sheets = ⌈(total area ÷ sheet area) × (1 + waste %)⌉.
Worked example
40 m² area, 1.2 m × 2.4 m sheets (2.88 m²), 10% waste. Sheets = ⌈(40 ÷ 2.88) × 1.1⌉ = 16 sheets.
Common mistakes
- Not accounting for cuts around doors, windows, and electrical boxes — add at least 10% waste.
- Ordering all sheets in one thickness — walls typically use 12.5 mm, ceilings 12.5 mm or 15 mm.
- Forgetting to order jointing compound and screws at the same time.
Frequently asked questions
How many drywall sheets do I need for a standard room?+
A 4 m × 3 m room with 2.4 m ceilings has roughly 40 m² of wall area. Using standard 1.2 m × 2.4 m sheets (2.88 m² each) with 10% waste, you need about 16 sheets. Always round up to the nearest whole sheet.
What thickness of drywall should I use?+
12.5 mm is the standard thickness for interior walls. Use 15 mm for ceilings to reduce sag between joists. Fire-rated areas may require two layers of 12.5 mm board.
How much waste allowance should I add for drywall?+
Use 10% for straightforward rooms. Add 15–20% for rooms with many windows, doors, or awkward angles that require more cuts. Each cut piece wastes the off-cut, so complex layouts need a higher allowance.
Do I need to order anything else along with drywall sheets?+
Yes — order jointing compound (approximately 5 kg per 10 m² of board), drywall screws or nails, corner bead for external corners, and joint tape. These are easily forgotten and will delay finishing if not ordered upfront.