Roofing Material Calculator

Replacing a residential or commercial roof is one of the most expensive maintenance projects a property owner will face. Ordering materials for a slanted, multi-pitched roof is significantly more complex than measuring a flat floor. The Calculay Roofing Calculator factors in the exact pitch (steepness) of your roof to accurately estimate the total surface area and the required number of architectural shingle bundles.

Understanding Roofing "Squares"

In the construction and roofing industry, materials are almost never sold by the individual square foot. Instead, contractors use a specialized measurement called a Roofing Square.

• 1 Roofing Square = exactly 100 Square Feet.
• If your total roof area is calculated at 2,400 square feet, you have a "24 Square" roof.
• Standard asphalt or architectural shingles are typically sold in "Bundles." It takes exactly 3 bundles of shingles to cover 1 Roofing Square. Therefore, a 24 Square roof requires 72 bundles.

The Importance of Roof Pitch

You cannot simply measure the footprint of your house (e.g., 40 ft by 60 ft = 2,400 sq ft) and order 24 squares of shingles. Because the roof is slanted upwards to shed water and snow, the actual physical surface area of the roof is significantly larger than the flat footprint of the house.

The steepness of this slant is called the Pitch, usually expressed as a ratio of Rise over Run (e.g., 6/12 means the roof rises 6 inches vertically for every 12 inches it runs horizontally).

• A flat roof (0/12 pitch) requires a multiplier of 1.00.
• A standard roof (6/12 pitch) requires a multiplier of 1.12. (A 2,400 sq ft footprint becomes 2,688 sq ft of actual roof surface).
• A steep Victorian roof (12/12 pitch) requires a multiplier of 1.41. (A 2,400 sq ft footprint becomes 3,384 sq ft of actual roof surface).

Accounting for Waste

Roofs feature valleys, ridges, hips, and dormers that require cutting shingles at complex angles, generating massive amounts of unusable scrap. Always order an extra 10% to 15% in materials to account for this inevitable waste, as well as to keep a few spare bundles in your garage for future storm damage repairs.