Sheathing Calculator

Ran the Roof calculator already? Keep Active project selected to reuse that area. Otherwise switch to Manual and type your own square footage.

Chained roof area

Run the roof calculator first to prefill sheathing with the active project roof area.

Areasq ftTotal area to cover, in square feet.

Only changes the default thickness suggestion and labeling below, not the sheet count.

Sheathing goes over rafters on a roof, or over studs on a wall — pick whichever this is.

Not sure? OSB is the more common, lower-cost choice; plywood is often preferred for roofs in high-moisture areas.

Sheet widthftPanel width as sold — standard sheet goods are 4 ft wide.Sheet lengthftPanel length as sold — standard sheet goods are 8 ft long.ThicknessoptionalinPanel thickness. Defaults to 7/16 in for roofs, 1/2 in for walls if left blank.Waste percent%Extra material to cover cuts and mistakes. 10% is typical.

You'll need — sheathing panels for — sq ft.

You'll need

Sheathing estimate

Warnings

INFO No roof area is saved in the active project yet, so the manual area is being used.
ERROR Enter an area greater than zero.

Detail values

Area used: — sq ft
Sheet area: — sq ft
Base sheets: —

Assumptions

Default panel size: 4 ft x 8 ft when unchanged
Sheathing spec: 0.4375" OSB for roof sheathing (not a code minimum — verify local requirements)
Estimated waste: 10% for an average project

Included: sheathing panels, waste allowance.

Not included: labor, delivery, permits, disposal of waste material.

Formula details

Sheet area: sheetWidth x sheetLength
Base sheets: area / sheetArea
Purchase sheets: ceil(baseSheets x (1 + wastePercent))

Material List

About this calculator

Use the active project roof area or a manual area entry to estimate sheathing purchase counts.

FAQ

Can I change the panel size from 4x8?

Yes. Both sheet width and length are editable so you can match the product you plan to buy.

Does this only work for roofs?

No. It works for any surface area as long as you enter the correct square footage.

Why is the purchase count rounded up?

Sheets are sold whole, so the calculator rounds up after the waste factor is applied.

What do Context and Material change?

Only the default thickness suggestion and the spec shown in the assumptions list — they don't affect the sheet count, which is driven purely by area and sheet size. Set them to document what you actually plan to buy.

Area source