How do I calculate how many roofing shingles I need?

Identify all roof planes, measure the length × width of each plane, add the areas for a total, apply a roof-pitch multiplier, then divide by the coverage per bundle and add a waste allowance.

What is the coverage per bundle of shingles?

A standard bundle covers roughly 33 sq ft. After applying your pitch multiplier, divide your total roof area by about 33 to estimate bundles.

Do I need to add extra shingles for waste?

Yes. Round up after your bundle calculation to account for cuts, breakage, and starter/hip/ridge pieces so you’re not short during installation.

How does roof pitch affect the number of shingles I need?

Steeper roofs require more material. Apply a slope multiplier to your total area before dividing by coverage per bundle.

Can GBR Roofing estimate my shingles for me?

Yes. GBR Roofing can inspect, measure, and provide an accurate material estimate for your San Rafael home. Call (855) 478-3292.

How Many Roofing Shingles Do I Need for San Rafael, CA Homes?

GBR Marketing
Apr 7, 2025
2 min read

Updated: Apr 11, 2025

A photo of a roof shingles with a blog title "How many roofing shingles do I need?"

Calculating the amount of roofing shingles you will need for a shingle replacement can seem like a daunting task. Fortunately, you will not need to climb a ladder and count the shingles on your San Rafael, CA. Home. Here is how you can calculate the number of shingles you will need.

How to calculate how many roofing shingles do I need?

Calculating the amount of roof shingles you will need for your roofing project requires some simple math. Follow this step-by-step guide to get an accurate estimate.

1. Identify the Planes of your Roof

The first step in calculating the number of shingles you will need is to find the total area of your roof. Start by identifying how many planes are present on your roof. A plane is a flat square section of roofing. For example, if you have a simple A-frame roof with no additional overhangs, you will have two planes.

2. Find the Area of Each Pane

After you have identified the individual planes that make up your roof, you will need to find the area of each plane. You can find the area by multiplying the length of the pane by the width of the pane. This will give you the square footage of each pane on your roof.

3. Calculate the Total Area of your Roof

Once you have measured the area of each of your planes you can find the total area of your roof by adding each plane’s area together.

4. Factor in the Pitch of Your Roof

The pitch, or steepness, of your roof will also affect the number of shingles you will need. To determine the additional shingles you will need for your slope, you will need to apply a multiplier to the total area of your roof. You can find roof slope multiplier tables online or follow the general rule of adding 5% per 10 degrees of pitch. Once you determine what your roof slope multiplier is, you can multiply it by the total area of your roof to determine the number of shingles you will need.

5. Consider Standard Coverage

Now that you know the total area and slope of your roof you can calculate how many bundles of shingles you will need. A standard bundle of shingles covers roughly 33 square feet. Divide the total area of your roof with the slope multiplier by 33 to see how many bundles you will need.

6. Round Up for Waste

Once you divide the total area by 33, round the number up to account for any broken shingles and additional coverage. It is always better to have slightly more than you need instead of not enough.

Let GBR Roofing Do the Math

Instead of calculating the number of shingles you’ll need to reroof your San Rafael home, trust the experts at GBR Roofing to do the math for you. Our certified roofers will ensure that your roof is done the right way. Contact GBR Roofing for a consultation and expert roofing solutions tailored to your needs. Call us at (855) 478-3292 or visit our North Bay location at 2175 Francisco Blvd E, San Rafael, CA 94901 to learn more!