Roof Shingle Calculator

Estimate pitched roof surface area, roofing squares and asphalt shingle bundles for one or more roof sections.

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How to Use the Roof Shingle Calculator

Enter each section’s horizontal plan length and width in feet, including overhangs that should be covered. Do not enter a measured slope length. Select pitch as rise in inches per 12 inches of horizontal run. Add separate, non-overlapping sections where needed, then choose waste and bundle coverage in square feet before calculating.

Formula and Explanation

Slope factor = √(1 + (pitch rise ÷ 12)²)
Roof surface = Σ(plan length × plan width × slope factor)
Roofing squares = roof surface ÷ 100
Bundles = ceil(roof surface × (1 + waste ÷ 100) ÷ bundle coverage)

For a simple roof section with uniform pitch, slope factor = √(1 + (pitch rise ÷ 12)²). Surface area = horizontal plan length × width × slope factor. Sum section surfaces; one roofing square is 100 sq ft. Coverage area = surface × (1 + waste ÷ 100). Bundles = ceiling(coverage area ÷ product coverage per bundle).

Use separate sections for distinct pitches without overlapping their plan areas. The pitch selector supports 0/12–24/12; selecting a pitch does not establish that a shingle product is suitable for it. This simple pitch model does not resolve complex roof geometry, valleys or dormers. Bundle coverage varies by product; verify it on the package. Starter strips, ridge caps, underlayment, flashing and accessories are separate. Estimates are planning quantities, not guaranteed purchase amounts or installation advice.

Worked Example

A 30 × 40 foot horizontal footprint at 6/12 pitch has a factor of √1.25 ≈ 1.118034. Roof surface is about 1,341.64 sq ft, or 13.42 roofing squares. Adding 10% waste gives about 1,475.80 sq ft. At 33.33 sq ft per bundle, round up to 45 bundles.

Frequently Asked Questions

Are length and width measured on the roof slope?

No. Enter the horizontal plan footprint of the section. The pitch factor adjusts that area to the sloped surface. Entering slope dimensions would apply the slope adjustment twice.

What does a 6/12 pitch mean?

It means the roof rises 6 inches for every 12 inches of horizontal run. Its slope factor is the square root of 1 + (6 ÷ 12)². Select each section’s own pitch if sections differ.

How many bundles cover one roofing square?

A roofing square is 100 sq ft, but bundles vary by product. A default of 33.33 sq ft is approximate and slightly less than one third of a square. Enter the manufacturer’s coverage rather than assuming exactly three bundles per square.

Are ridge caps and starter strips included?

No. This estimates field-shingle coverage plus your waste allowance. Ridge caps, starter strips, underlayment and other materials need separate product-specific planning.