Plywood / OSB Calculator — m to sheets, cost
How to use this calculator
Pick a shape — Rectangle, L-Shape, or paste a known area in m². Choose the panel size (1220×2440 mm is the European standard; 1250×2500 and 1525×3050 for specials), thickness, and material. The number you order drives your delivery — net sheets is theoretical; the headline rounds up after waste because merchants only sell whole panels.
Sheathing rule of thumb: 12 mm OSB for walls, 15 mm for roofs, 18–22 mm T&G for floors over joists at 400 mm c/c. Bump waste to 15–20% for hip roofs, dormers, or rooms with lots of trim cuts.
Saved Calculations
| Time | Shape | Area m² | Material | Thick | Sheets | Weight | Cost |
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How to Use the Metric Plywood / OSB Calculator
Enter dimensions in m, cm, or mm for a rectangle or L-shape (footprint minus a cutout), or type a known area in m². Choose the panel size, thickness, and material, then set a waste factor for trim and fitting. Net sheets is the bare area divided by panel coverage; the purchased figure rounds up after adding waste, because you buy whole panels.
Formulas
Net sheets = area ÷ (panel length × panel width). Purchased = ceil(net × (1 + waste%)). A 1220×2440 mm panel covers 2.98 m²; 1250×2500 = 3.13 m², 1525×3050 = 4.65 m². Panel weight = density × (panel area × thickness/1000), using plywood ≈550, OSB ≈600, MDF ≈750 kg/m³.
Sheet Sizes, Thickness & Waste
Per EN 636 (plywood) and EN 300 (OSB), the European standard panel is 1220×2440 mm — the metric equivalent of 4×8 ft. Common thicknesses: 9 mm (backing/sarking), 12 mm (walls), 15 mm (subfloor), 18 mm (structural subfloor and sheathing), 21–27 mm for heavy-duty floors per Eurocode 5 spans. Use 10% waste for plain sheathing, 5% for simple rectangles, and 15–20% for cut-up roofs.
Related Calculators
Plan the structure under these panels with the floor joist span calculator and estimate framing with the lumber volume calculator or the stud wall calculator. For outdoor work, see the deck calculator and fence calculator. Working in feet and inches? Use the imperial plywood / OSB calculator.
Ordering tips
Three calls that ruin a panel takeoff. Stagger the joints — EN 12369-1 and BS 8103 expect ½-sheet offset on roofs and floors, so order 1–2 extra sheets beyond the rounded number for the end pieces. Match grade to job — OSB/3 (≈€15–35 per 18 mm 1220×2440 in 2025) is fine for walls and roofs; structural plywood EN 636-2 S (≈€25–50) is what you use for floors and damp areas; MDF (€20–40) is dry interior only, never under tile or in a bathroom. Use H-clips or T&G edges — roof sheathing at 600 mm c/c needs H-clips at panel mid-spans; subfloors over 600 mm c/c joists need 22 mm T&G, not 18 mm square-edge. Buying a full pack (40–60 sheets) is usually cheaper per panel than a loose count — ask the merchant.
FAQ
Does the count include waste? Yes — "Sheets Needed" adds your waste percentage and rounds up to whole panels. "Sheets (net)" is the theoretical minimum with no offcuts.
Why is OSB heavier than plywood? OSB is denser (≈600 vs ≈550 kg/m³); MDF is heaviest at ≈750 kg/m³. An 1220×2440 × 18 mm sheet runs roughly 25–30 kg plywood, 28–33 kg OSB, 38–44 kg MDF.
How accurate is the cost? It is sheets × your price per panel in the selected currency. Confirm a current quote, grade, and thickness before ordering.
