Roofing Calculator - Squares & Bundles Needed

  • Flat / Low (×1.06)
  • Medium 6/12 (×1.12)
  • Steep 9/12 (×1.25)
  • Very Steep 12/12 (×1.41)
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Estimate the shingles your roof needs with our Roofing Calculator. Enter the roof's footprint length and width, select the pitch, and get the actual roof surface area, the number of roofing squares, and the bundles of shingles required.

Roof pitch matters because the sloped surface is longer than the horizontal footprint — the calculator applies a multiplier from ×1.06 (low slope) up to ×1.41 (12/12 pitch). Shingles are sold by the "square" (100 sq ft), with three bundles covering one square for most asphalt products.

A 10% waste factor suits simple gable roofs; hips, valleys, and dormers push it to 15%. Starter strips, ridge caps, and underlayment add to the total. Always verify measurements on-site before ordering, since roof measurements from the ground are approximations.

สูตร
roof area = footprint × pitch multiplier | squares = area ÷ 100 | bundles = ceil(squares × 3 × (1 + waste%))

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What is a roofing square?
A roofing square is 100 square feet of roof — the standard unit shingles are sold in. Three bundles of asphalt shingles typically cover one square.
How does roof pitch affect the area?
The roof surface is longer than its horizontal footprint. The calculator applies a pitch multiplier (from ×1.06 for low slopes to ×1.41 for 12/12) to convert footprint area to actual roof surface.
How many bundles of shingles per square?
Most asphalt shingles come three bundles per square (100 sq ft). Some heavier architectural shingles use four bundles per square — check your product label.
What waste factor should I use for shingles?
Use 10% for simple gable roofs and 15% for hips, valleys, and dormers. Starter strips and ridge caps also consume material, which the waste factor covers.

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