How many OSB sheets should you allow for?
The calculation uses the net area, including the area of a drawn plan when selected. It adds the waste allowance, divides by one sheet’s area and rounds up to a whole sheet.
Formula
Sheets = round up [area × (1 + allowance / 100) ÷ (sheet length × sheet width)]
Sheet cost = whole sheets × price per sheet
Worked example
Example assumptions: 20 m², a 10% allowance and €22 per sheet. The area including allowance is 20 × 1.10 = 22 m².
A 2.50 × 1.25 m sheet covers 3.125 m². 22 ÷ 3.125 = 7.04, rounded up to 8 sheets: 8 × 22 = €176. The allowance and price are illustrative, not recommendations.
Assumptions and limits
- This is an area-based estimate, not a cutting plan. Orientation, supports, openings and reusable offcuts can change the actual purchase quantity.
- The calculator does not specify sheet thickness, grade or fixings. The example includes sheets only, excluding labour and accessories.
Common questions
Why round up to 8 sheets instead of 7?
In the example, 7 sheets cover 21.875 m², less than the 22 m² including allowance. Rounding up covers the calculated area but does not prove that the sheets will fit your layout.
Which sheet dimensions should I enter?
Use the selected product’s usable coverage dimensions in metres. Check the product data, especially for tongue-and-groove sheets. Suggested sizes are editable presets, not a specification.