Roof Sheathing Calculator
Roof decking by plane: enter the footprint length (ridge direction) and horizontal width of one roof plane, pick the pitch, and set the number of identical planes (2 for a gable). Hips and valleys cut more — use 15% waste.
Order 44 sheets — units of 4 × 8 sheeting are 50 per lift; sheets are cheaper by the unit.
- Area
- 1,252 ft²
- Waste / cuts 10%
- + 125 ft²
- Coverage to buy
- 1,377 ft²
- Metric
- 116.3 m²
- 4 × 8 ft sheets (32 ft²)
- 44
- 4 × 10 ft sheets (40 ft²)
- 35
- Approx. weight
- 2,200 lb
- Nails / screws, 8d ring shank
- 7 lb
- Materials + delivery$18–$65 / sheet · Sep 2026
- $867 – $2,935
- Installed (with labor)typ. $3,674
- $2,119 – $6,691
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What will this plywood & osb job cost?
See the installed price range for these quantities and get up to 3 quotes from local contractors. Free, no obligation.
How to calculate plywood or OSB by hand
Sheets = Area (ft²) × pitch factor × (1 + waste) ÷ 32
Worked example
- Area: 24 ft × 16 ft = 384 ft² (a flat floor — pitch factor 1).
- Waste 10%: 384 × 1.10 = 422 ft².
- Sheets: 422 ÷ 32 = 13.2 → 14 sheets of 4 × 8.
- For a 6/12 roof over the same footprint: 384 × 1.118 = 429 ft² per side → 15 sheets per plane.
- 4 × 8 sheet
- 32 ft²
- 4 × 10 sheet
- 40 ft²
- Sheets per 100 ft², 10% waste
- 3.4
- Pitch factor 6/12 · 8/12 · 12/12
- 1.118 · 1.202 · 1.414
Questions crews ask
How many sheets of plywood for a roof?
Footprint of each plane × pitch factor ÷ 32 × 1.10. A 40 × 28 ft gable at 6/12 has two planes of 40 × 14 ft: 560 × 1.118 = 626 ft² each → 22 sheets per side, 44 total (about 1,375 ft² of roof, 13.75 squares).
What thickness for roof sheathing?
7/16″ OSB or 15/32″ plywood at 24″ rafter spacing is the code minimum for most asphalt-shingle roofs; ⅝″ (19/32) where rafters are 24″ o.c. with heavy tile or in high-snow areas. Use H-clips between rafters on 7/16″.
How many nails for roof sheathing?
8d ring-shank nails every 6″ on edges and 12″ in the field: about 60 nails per sheet, roughly 1 lb per two sheets. A 44-sheet roof takes around 25 lb.