How this is calculated
Wall area is the room perimeter times ceiling height: 2 × (length + width) × height. The ceiling is the floor rectangle. Openings are not deducted because offcuts from doors and windows rarely equal a full sheet, and leftover pieces are useful for soffits and patches.
Sheets are sold in fixed sizes. Dividing total area by one sheet and rounding up is how suppliers count an order. A waste allowance covers miscuts and damaged boards.
Formula & methodology
Wall area = 2 × (Length + Width) × Height. Ceiling = Length × Width (if included). Total with waste = (walls + ceiling) × (1 + waste %). Sheets = Total ÷ sheet area, rounded up.
Worked example
A 16 ft × 12 ft room, 8 ft ceilings, walls and ceiling, 10% waste, 4×8 sheets
- 1.Wall area = 2 × (16 + 12) × 8 = 448 ft²
- 2.Ceiling = 16 × 12 = 192 ft²
- 3.Gross = 640 ft²; with 10% waste = 704 ft²
- 4.Sheet area = 32 ft²; 704 ÷ 32 = 22 sheets
Frequently asked questions
Should I deduct doors and windows?
You can mentally subtract large openings, but most hangers still round up to full sheets. This calculator does not deduct openings so you are less likely to run short.
What sheet size does this assume?
US: 4×8 ft (32 ft²). UK: 1200×2400 mm. If you are hanging 4×12 ft boards, you will need fewer sheets for the same area — divide the coverage figure by 48 ft² instead.
Does this include joint compound and tape?
No — only boards. Compound, tape, screws, and corner bead depend on the finish level (typically 3–5) and should be listed separately.
How much waste should I add?
Ten percent is reasonable for a rectangular room. Use 15% if there are many corners, arched openings, or you are hanging for the first time.
Last updated 2026-08-01. Formulas are planning methods — confirm with a supplier before you order.