A roofing square represents 100 square feet of roof surface. To estimate field-shingle bundles, divide the measured sloped area by 100, then multiply by the coverage listed for the shingle product. Bundle counts vary by product, so do not assume every square uses the same number of bundles.
Convert measured roof area to squares
Start with the roof’s sloped surface area, not just the building footprint. If you have a verified total in square feet, divide by 100. For example, 2,240 square feet is 22.4 roofing squares. This unit conversion describes area; it does not include a material allowance.
If you only have a horizontal footprint, slope and overhangs affect the surface area. Estimate those first with the Roof Area Calculator. For a roof with different pitches or several planes, measure and total the planes using an appropriate method rather than applying one pitch to all of them.
Use the shingle package coverage
Check how many square feet or how many bundles the selected package covers. If its listed coverage is expressed as bundles per square, multiply that number by the square count. If coverage is given per bundle, divide the area by that coverage and round up to a whole bundle. Follow the package instructions for the exact product and exposure.
Example: A measured 2,240-square-foot roof is 22.4 squares. If the selected package information says three bundles cover one square, the base estimate is 22.4 × 3 = 67.2 bundles, rounded up to 68. That example uses an assumed product coverage; another shingle can have different coverage.
Add an allowance only after the base estimate
Hips, valleys, dormers, cut patterns, breakage and the installation method can affect how much material is needed. If you use a waste percentage, treat it as a project planning input and confirm it with the installer or supplier. Starter strips, ridge caps, underlayment and other accessories are separate quantities and cannot be inferred from field-shingle bundle coverage alone.
For a quick estimate, enter the measured area, package coverage and chosen allowance in the Roofing Material Calculator. The existing guide on how pitch changes roof area explains the area step.
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