A sheathing calculator is the wall area calculator applied to a 4 by 8 sheet: the square feet of wall, roof or floor to be covered, divided by 32, plus the contractor's waste allowance for the cuts at openings, corners and roof edges. It is the same sum whether the sheet is plywood or OSB and whether it is written sheathing or sheating in the search box, and it is the sum behind how many sheets of plywood do I need for a wall, a roof deck or a subfloor. This page works a 24 by 9 foot wall, a roof deck and a subfloor, says how boards are counted when the covering is boards rather than sheets, and prices the result with the lumber cost calculator at the yard's own prices; the free construction cost estimator on this site carries the line into the estimate, with no account.
How many sheets of plywood do I need: the wall
Sheets equals the area in square feet divided by 32, the area of a 4 by 8 sheet, plus waste, rounded up. A 24-foot wall sheathed 9 feet high is 216 square feet; divided by 32 is 6.75 sheets, and with a 10% allowance for the cuts at the corners and the band it is 7.4, so 8 sheets. Openings are usually left in, because the sheet is cut around them and the offcut is rarely reusable; a wall that is mostly opening is the exception. The APA publishes the span ratings and the panel standards the sheet is specified against; the count is the calculator's, and it should return whole sheets by the size the yard stocks, 4 by 8 or 4 by 9 for a 9-foot wall to save a course of cuts.
The roof deck and the subfloor: the same sum with more waste
A roof deck's area is the plan area divided by the cosine of the pitch, or more simply the rafter length times the ridge length for each plane: a 30 by 40 foot building with a rafter length of 22 feet on each side is 2 times 22 times 40, 1,760 square feet, 55 sheets before waste and 61 at 10%, more on a hipped or cut-up roof where the diagonal cuts throw away more of each sheet. A subfloor is the floor's plan area over the joists: a 30 by 40 foot floor is 1,200 square feet, 37.5 sheets, 42 at 10%. The how many sheets of plywood do I need calculator is the same division with the waste allowance set for the surface; the roof gets the higher one.
How many boards do I need: when the covering is boards, not sheets
For a board covering, siding, a deck or a board subfloor, the count is the area divided by the exposed face of one board: a board with a 5.5-inch exposed face covers 0.458 square feet per linear foot, so 216 square feet of wall needs 471 linear feet of board, plus waste, ordered in the lengths the yard sells. The how many boards do I need calculator therefore needs the board's exposed width and the lengths available, and it returns pieces by length, not a bare count. A wood calculator for project that returns a total in square feet has done the area and left the ordering to the yard.
The lumber cost calculator: the sheets and boards priced, and into the estimate
The lumber cost calculator is the count times the yard's price per sheet or per board, with the fasteners as their own line: 8 sheets at the yard's price, 471 feet of board at the yard's price per foot, nails by the pound, and the contractor's labor to install at their own rate. Added and marked up at the contractor's overhead and profit, that is the sheathing or siding line in the estimate. The free construction cost estimator on this site carries the line at the contractor's own cost per square foot with site work, contingency and overhead and profit shown, and the schedule of values carries it as the value of that work for the draw.
Questions people ask about sheathing calculator
How many sheets of plywood do I need for a 24 by 9 wall?
216 square feet divided by 32 is 6.75 sheets; with a 10% waste allowance, 8 sheets of 4 by 8, or 6 of 4 by 9 to avoid a course of cuts.
How much waste does a sheathing calculator add?
The contractor's own allowance: around 10% on a plain wall or floor, more on a cut-up or hipped roof where the diagonal cuts waste more of each sheet. Openings are usually left in the area.
How do I count boards instead of sheets?
Area divided by the board's exposed face width in feet gives linear feet, plus waste, ordered in the lengths the yard sells. A 5.5-inch face covers 0.458 square feet per foot.