Sheathing calculator
How many 4×8 sheets of plywood or OSB for a building's walls, its roof or a subfloor — the roof worked out from the footprint and the pitch, with the H-clips it takes.
Along the ridge
Eave to eave
Rise per foot of run
Past the wall, every side
Offcuts at the ends and around openings, 10% is usual
4×8 sheets of roof sheathing
54sheets
Area covered
1543 sq ft
With waste
1697 sq ft
H-clips
196
Where the number comes from
- Plan areaFootprint grown by the overhang on every side
- 1380 sq ft
- Slope factorAt 6:12 — the same factor the roofing calculator uses
- 1.1180
- Sheathed areaFootprint with overhang, times the slope factor
- 1543 sq ft
- 4×8 sheets1697 sq ft with 10% waste, at 32 sq ft a sheet
- 54
- H-clips4 per installed sheet — one in each 24" bay along its long edge
- 196
Where H-clips go, and whether you need them
APA's rule for roof panels that need their long edges supported is one clip midway between each pair of rafters, along the joint between one course of sheets and the next. A 4×8 laid across rafters at 24" on centre crosses 4 bays, so it takes 4 clips. Clips also hold the 1/8" gap between sheets that the panel makers ask for.
Whether your panel needs edge support at all depends on its thickness and the span rating stamped on it — check the stamp against the APA span table, and ask your building department, rather than taking this page's word for it.
Where to buy this
- 54 sheets roof sheathingHome DepotLowe's
- 196 H-clipsHome DepotLowe's
This searches the material, not a thickness or span rating we worked out for you — the rafter or joist spacing and the panel's stamp decide that.
Plain search links, nothing sponsored. Prices and stock are the shop's, and a local lumberyard will usually beat both on solid stock.
About sheathing quantities
- How many sheets of plywood do I need for a roof?
- Take the footprint, add the overhang on every side, and multiply by the slope factor for the pitch — 1.1180 at 6/12. A 28' x 44' house with a foot of overhang is 1380 sq ft of plan and 1543 sq ft of roof, which with 10% waste is 54 sheets of 4x8 at 32 sq ft each.
- How many H-clips per sheet of roof sheathing?
- APA's rule for roof panels whose long edges need support is one clip midway between each pair of rafters, along the joint between one course of sheets and the next. A 4x8 laid across rafters 24" on centre crosses 4 bays, so that is 4 clips per sheet; at 16" on centre it is 6. Whether a panel needs edge support at all depends on its thickness and span rating — read the stamp against the APA span table rather than assuming.
- Should I subtract windows and doors from wall sheathing?
- Only if you are going to cut the sheets around them. Many framers sheathe straight over the openings and cut them out with a router afterwards, and then the cut-outs are simply waste. The calculator's example — 28' x 44' with 8' walls and 120 sq ft of openings — comes to 36 sheets with the openings taken off; enter 0 for the openings if you will sheathe over them.
- Is a hip roof more sheathing than a gable?
- Not in area: at one pitch over the same footprint, a hip roof and a gable have the same sloped area, because every plane rises at the same rate over the same plan. A hip wastes more, though — every hip line is a row of angled cuts — so raise the waste figure to 15% or so for a hip and more for a roof with valleys or dormers.
You might also need
- Roofing calculatorSquares, bundles, starter strip, ridge cap and underlayment from a building footprint and a pitch.
- Wall framing stud countField studs at 16" or 24" on centre, corner studs, and the king and jack studs every opening adds.
- Fastener calculatorScrews or nails for a sheet good on an edge-and-field pattern, with the box count to buy.