Roof Sheathing Calculator

Use the roof sheathing calculator to estimate the number of sheathing panels required to cover a roof.

How to Calculate Roof Sheathing Requirements

Estimating the correct number of roof sheathing panels for a project is vital to ensuring a smooth construction process, budget efficiency, and reducing wastage. To accurately determine the amount needed, contractors must consider two main factors: the surface area of the roof and the pitch.

1. Measuring the Surface Area

The surface area of the roof is the starting point for all estimations. Measure the length and width of each roof section (or plane), and multiply them together to get the area of that section. 

For instance, if one side of the roof measures 20 feet in length and 30 feet in width, its area is 600 square feet. Repeat this for all sections and add them up to get the total surface area.

2. Correcting for Roof Pitch

The pitch of the roof affects the actual surface area that needs to be covered. A steeper pitch means more surface area than a flat roof with the same base dimensions.

Here's a table of common roof pitches and their corresponding multipliers:

To apply the multiplier, multiply the total base surface area by the value corresponding to your roof's pitch. For example, with a 6:12 pitch on a 600-square-foot area, the adjusted area is 600 x 1.12 = 672 square feet.

3. Sheathing Panel Dimensions and Applications

Roof sheathing panels are typically sold in dimensions of 4 ft x 8 ft. This is the standard size for most residential and commercial projects. With an area of 32 square feet, it's easy to calculate how many panels you'd need by dividing the total square footage by 32.

Thickness

Commonly, sheathing panels are available in 7/16", 1/2", and 5/8" thicknesses. The choice depends on the building codes in your area and the roofing material you'll use.

• 7/16 in. is suitable for shingle roofs in most residential applications.
• ½ in. sheathing is used for heavier roofing materials or where building codes require it.
• ⅝ in sheathing is preferred for areas with high wind or snow loads.

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