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Use the asphalt shingle calculator to estimate the amount of material required to cover a roof.

How to Estimate Asphalt Shingle Needs

This article will guide you on how to effectively gauge the number of asphalt shingles required, along with other essential materials.

1. Measure the surface area.

The first step is to determine the surface area of the roof. This is typically done by measuring the length and width of each roof section and multiplying these two figures. For instance, if one side of the roof is 30 feet long and 20 feet wide, its surface area is 600 square feet. Calculate the surface area for each section and then sum them up for the total surface area.

However, roofs often have extra elements like gables, dormers, or valleys. These additional structures can affect the surface area significantly. Gables, for instance, can be calculated as triangles, with the base being the width of the gable and the height (from base to apex) being the other necessary measurement. Measure and calculate the surface area of these elements separately, then add them to the total surface area of the primary roof sections.

After considering all sections and elements, sum them up to determine the total surface area.

2. Adjust for the roof pitch.

A roof's pitch, or its slope, can significantly influence the amount of materials needed. A steeper pitch means a larger surface area than what's visible from a bird's-eye view.

To adjust for the pitch, use a pitch multiplier. Below is a table of common roof pitches and their multipliers.

For instance, if your roof pitch is 6:12 and the measured surface area is 2,000 square feet, you'd adjust for the pitch as: 2,000 x 1.12 = 2,240 square feet.

3. Understand asphalt shingle sizes and bundle quantities.

Asphalt shingles typically come in two main sizes:

• 3-tab shingles are usually 12 x 36 inches.
• Architectural shingles vary but are often about 14 x 39 inches.

A standard bundle of asphalt shingles will typically cover around 33.3 square feet. So, for a roof area of 2,240 square feet (from our previous example), you'd need around 67 bundles (2,240 ÷ 33.3). 

Always round up to ensure you have enough materials, and consider purchasing an extra bundle for mistakes or future repairs.

Other Essential Roofing Materials

Underlayment

This protective layer sits between the roof deck and the shingles. For asphalt shingles, #15 felt (often used for lower-slope roofs) or #30 felt (used for steeper slopes) are common choices. You'll need enough underlayment to cover the entire roof, so using our 2,240 square feet example, you'd require roughly 7 rolls of #30 felt (each roll usually covers about 432 square feet).

Fasteners

You will generally need four nails per shingle for standard installations, and up to six nails for high-wind areas. If you're using 3-tab shingles, that's roughly 320 nails per bundle. So, for 67 bundles, that's approximately 21,440 nails.

Sealant

A vital component in roofing, sealant is used to ensure watertight seals around vents, chimneys, skylights, and other protrusions. It also provides added protection at the shingle edges, especially in high-wind zones. Typically, one tube of sealant can cover approximately 25-30 linear feet when applied in a 1/4" bead. 

Estimate the length of all seams, junctions, and edges requiring sealant, then divide by the coverage provided by one tube to determine the number of tubes needed. Always purchase a couple of extra tubes to account for potential wastage or other unexpected needs.

Estimating the quantity of asphalt shingles and related materials requires precise measurements and adjustments for unique roof characteristics. Using the steps above, contractors can confidently approach their roofing projects with the right materials in tow. Remember to always factor in a margin for error or unforeseen challenges that may arise during the installation process. 

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