Roof Sheathing Calculator
Count OSB or plywood sheets for a new roof or a re-deck, with H-clips and nails.
How it's calculated
The calculator finds the sloped roof area from the house size, overhang and pitch, adds waste, and divides by 32 sq ft per 4×8 sheet.
With 24" rafters or trusses, H-clips go between supports on the unsupported long edges, one per bay. Nails are counted at 6" on center at panel ends and 12" at intermediate supports.
Worked example
A 1,860 sq ft roof with 10% waste needs 1,860 × 1.10 ÷ 32 = 64 sheets. On 24" trusses that is 256 H-clips.
Field notes
- Stagger panel end joints by at least one rafter bay.
- Run the long dimension across the rafters, never parallel to them.
- Leave 1/8" between panels for expansion.
- High-wind zones often require 6" nailing in the field and ring-shank nails.
Common questions
- How many sheets of OSB do I need for a roof?
- Divide the roof area in square feet by 32 and add about 10% waste. A 2,000 sq ft roof takes about 69 sheets.
- Do I need H-clips?
- Usually yes with 7/16" or 15/32" panels over 24" spacing. Check the span rating stamped on the panel.
- What thickness roof sheathing should I use?
- 7/16" OSB is the minimum common choice for 24" spacing. 1/2" or 5/8" plywood stiffens the roof and holds nails better.