Plywood Calculator
Calculate how many sheets of plywood, particleboard, OSB or structural sheeting you need for any floor, wall, roof or formwork area. Get sheet count, lineal metres and cost instantly.
🔨 Plywood Calculator
📐 How It Works
Sheet count is calculated by dividing the total area by the coverage area of each sheet, then adding a waste factor for cuts and off-cuts. The waste factor depends on the layout — simple rectangular areas need 10%, complex shapes with many cuts need 15–20%.
📋 Worked Example
Subfloor for a 9m × 7m house: Area = 63 m². Sheet area = 2.88 m². With 10% waste: 63 × 1.10 ÷ 2.88 = 24.1 → order 25 sheets of 2400×1200mm structural plywood.
❓ Frequently Asked Questions
Residential subfloor on joists at 450mm: 19mm structural plywood minimum. Joists at 600mm: 22mm minimum. Sheet flooring (particleboard): 19mm for 450mm joist spacing. Always check the manufacturer's span table for your specific joist spacing and load.
Structural plywood has cross-laminated wood veneers giving strength in both directions. Particleboard (chipboard) is cheaper but weaker, especially against moisture. Use structural plywood for wet areas, roofs and high-load applications. Particleboard suits dry internal floors and cabinetry.
Plan your sheet layout before cutting. Start from the straightest wall. Run sheets perpendicular to joists and stagger end joints. Use off-cuts for small areas. A simple room with few cuts may only need 5–7% waste while a complex shape with many angles may need 20%.
Structural plywood used in wet or exposed conditions should be H3 treated (for exterior above ground) or H4/H5 for in-ground or very wet conditions. Internal dry areas can use untreated F11 or F14 grade. Check the application requirements with your supplier.