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Calculating Materials
Asphalt Shingles

Go back to Estimating Materials

This page was designed to help you figure asphalt shingle material quantities according to roof size and other criteria. RoofHelp was very careful in designing this page but please understand it is for informational purposes only. We cannot possibly guarantee 100% accuracy in any way, shape, or form because each roofing project is unique and all variables cannot be accounted for.

Roof Size

Don't know how to measure your roof? No problem, simply click here.

Enter roof size in square feet. RoofHelp will automatically round off the number and add five percent to accommodate material waste.

Type only the number. Don't add any extra items such as a quote mark (') or "ft." For example, if your roof is 2,500 square feet, type in only the number 2500, not [2,500'] or [2500 sq. ft.], or [2500 ft.].

Type of Project

Is this an overlay or are you tearing off the existing roof?
Tear Off

Strong Wind Area

This is important because it will determine the proper nailing pattern for the shingles and the felt underlayment. Strong winds (usually in excess of 50 MPH) can rip shingles off of a roof if they aren't fastened properly or haven't had time to seal. Aggressive nailing of the shingles and felt can help reduce damage.

Click here if you live in a high wind area:
Yes, winds in my area can exceed 50 MPH.

Roofing Nails

Your roofing nails should be long enough to penetrate your roof deck 3/4" or they should go all the way through your deck if it's less than 3/4". For instance, if you have 1/2" plywood for a roof deck, your roofing nails should go all the way through and poke out in the attic. Please be advised that it can be difficult to find roofing nails longer than 1-3/4" in length.

Are you still not too sure about what length to use? No problem, simply click here for some suggestions.

Please choose the length of roofing nail you plan on using:

If you're using a coil nail gun to install your shingles, then you don't need to tell us the length of roofing nail you're using. Coil nails are figured by quantity, not weight. RoofHelp will automatically calculate the amount of coils you need. Unfortunately, most roofing material supply places don't sell coil nails by the individual coil, you have to purchase them by the box. Most boxes contain 27 or 36 coils.

Felt Underlayment

Felt underlayment is that black tar paper stuff you see roofers putting on prior to installing the shingles. There are two basic types used for underlayment - #15 Felt and #30 Felt. Both consist of organic felt saturated with asphalt. #15 starts as a dry organic felt weighing around four pounds per 100 square feet and the #30 felt weighs nine pounds per 100 square feet. Both are saturated with asphalt for a final weight of about eight pounds and twenty pounds per 100 square feet, respectively. #15 comes in rolls three feet wide and 144 feet long (four roof squares per roll) while #30 rolls are roughly half that length (two roof squares per roll).

When considering felt underlayment, you will need to know your roof's slope. Click here to see how to measure your slope. Here are RoofHelp's recommendations for felt usage:
1. If your slope is between 3" in 12" (3:12) and 4" in 12" (4:12), use two layers of #15 felt.
2. If your slope is greater than 4" in 12" (4:12), use one layer of #15 felt.
3. The use of #30 felt is strictly your choice. RoofHelp does not think it's necessary for asphalt shingles and does not recommend it if you are using a lightweight shingle weighing 240 pounds per square or less. If you are unsure of the shingle weight, you'll need to contact the manufacturer of the shingles.

Choose the type of felt underlayment you are going to use:
#15 Felt - One Layer
#15 Felt - Two Layers
#30 felt - One Layer

Underlayment Nails

Underlayment nails should follow the same criteria as roofing nails when determining length. As a general rule, you should consider using 3/4" underlayment nails if you have a 3/8" or 1/2" wood deck and 1" nails if your roof deck is 5/8" in size or greater. Most houses have 1/2" plywood or OSB, but some older homes will have 1x6 or 1x8 planks. only calculates underlayment nails in accordance with the fastening patterns found by clicking HERE. These are fastening patterns recommended by both roofing material manufacturers and by the National Roofing Contractors Association. All information is based on the specifications of nails manufactured by Simplex Nails.

Choose the type of nail you want to use for your felt underlayment:
Square Head (Not available in 1/2" or 2" lengths)
Round Head
Plastic-Cap (Not available in 1/2" length)

If you are going to use Plastic Cap nails, then you can skip this next part. Plastic cap nails are purchased according to nail count, not weight, and are available in boxes of 200 or so.

Nails are available in lengths of up to three inches but you shouldn't need nails longer than 2" and in most cases the nails won't be longer than 1-1/4". The longer ones are usually only used when roof insulation is installed, or for other types of construction.

Choose the length of nail you plan on using for the underlayment so RoofHelp can calculate approximately how many pounds of nails you'll need:

Ice Dam Protection

Do you live in an area where the average January temperature is below freezing? If so, then you need to install an ice and water protection membrane to your roof. These are commonly referred to as ice shields, ice guards, ice and water shield (which is the trade name used by Grace, a manufacturer), and sometimes water shields. They are typically available in thicknesses of 25 mils (.025") to 40 mils (.040"). The rolls are typically thirty-six inches (36") wide and thirty six feet (36') or seventy-five feet (75') long.
For more information on ice dams and how much you'll need, visit the RoofHelp library at or visit some manufacturers' web sites by going to the Roofing Products Page of and clicking on the Ice Dam Protection link in the left frame.

Hip and Ridge Cap

If you plan on purchasing premade hip and ridge cap, then simply measure your hips and ridges, add five percent for waste, and tell the material supplier how much you need and they'll order it for you.

If you plan on cutting your own hip and ridge cap from regular 3-tab shingles, then simply type the lineal feet you need in the box below.

Type only the number. Don't add any extra items such as a quote mark (') or "ft." For example, if you have eighty-nine feet of ridge, type in only the number 89, not [89'] or [89 feet], or [89 ft.].

Nails for the Hip and Ridge Cap

The nails you'll need for your hip and ridge cap will be longer than those you need for your roof - usually a half inch longer or so. RoofHelp will calculate the amount of nails you need depending on the length of roofing nail and how much hip and ridge you have.



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