Measure walls and sheets
Measure the room walls, subtract doors and windows, and enter the dimensions of the sheets you plan to buy. Add your chosen waste allowance and a price per sheet.
Worked example
Example: a 14 × 11 ft room with 8 ft walls has 400 sq ft of wall area. Subtract 42 sq ft of openings and add a chosen 10% allowance: 393.8 sq ft. With 4 × 8 ft sheets, round up to 13 sheets. At an example price of $18 per sheet, the estimated cost is $234.
The formula
Sheets = round up [(wall area − openings) × (1 + waste ÷ 100) ÷ sheet area].
Before you buy
This is an area-based estimate. Check your cutting layout before buying: the layout can require more sheets. This example covers walls only, without the ceiling. Estimate different sheet sizes separately. Fasteners, jointing materials, delivery, and labour are additional costs.
Keep the result in FixCalc
FixCalc is free to download. All calculators and complete results are free. Free saves up to 3 estimates in 1 project. FixCalc Pro Lifetime is one purchase for unlimited projects and saved estimates plus shopping-list PDF export.