How Many Shingles Cover a Square of Roofing
Installing a new roof is a major project that requires careful planning and preparation. One of the most important calculations you need to make is determining how many shingles you will need to complete the job. The standard unit of measurement in roofing is a "square," which refers to 100 square feet of roof area. By calculating the total number of squares on your roof and then figuring out how many shingles are needed per square, you can estimate the total shingle requirements with reasonable accuracy.
Getting an accurate shingle estimate helps you budget for materials, plan the project timeline, and ensure you purchase enough supplies in your initial order to avoid shortages later. With some basic math and an understanding of a few key roofing measurements, you can break down this critical roofing quantity and get your shingle count right.
What is a "Square" in Roofing?
In the roofing industry, a "square" is defined as an area of 100 square feet. Roofing squares serve as a standard unit of measurement to make it easier to calculate materials and estimate costs for different roof sizes and shapes.
Some key facts about roofing squares:
- One square = 100 square feet of roof area
- Total roof square footage can be calculated by length x width measurements
- The number of squares then tells you how many bundles of shingles are needed
For example, if a simple rectangular roof measures 40 feet long by 32 feet wide, the total area would be 40 x 32 = 1,280 square feet. Dividing by 100 tells us the roof has 12.8 squares. Roughly 13 squares worth of shingles would be required to cover this roof.
Why Squares Simplify Shingle Estimates
Roofing squares provide a useful shorthand for making quick calculations. Some key reasons squares help determine shingle requirements:
- Shingle bundles are designed to cover 3 squares
- The number of squares tells you how many bundles are needed
- It's easier than working with large total square footages
By converting the total roof area to squares, you can immediately get an idea of the number of shingle bundles required. This saves time and avoids mistaken estimates. Understanding squares is essential for both DIYers and roofing pros.
Shingles per Bundle and Coverage
When estimating your shingle needs, you also need to know how many shingles come in each bundle. The number per bundle, and the coverage area provided, depends on the shingle type:
- 3-tab shingle bundles contain approximately 27-36 strips
- Architectural/laminated shingle bundles have 18-36 shingles
- 1 bundle covers around 33.33 square feet of area
Additionally, the exposure size of the shingle impacts how much of the roof a single shingle covers. Exposure refers to how much of the shingle is exposed to the elements. Typical exposures are 5", 5.5", or 7".
Importance of Exposure Measurement
The exposure measurement is key because:
- Lower exposures like 5" require more shingles per square
- Higher 7" exposures reduce the number of shingles needed
- Exposure impacts the number of shingles per bundle
When estimating, always confirm the manufacturer's specified shingles per bundle and exposure size. This provides the data needed for accurately calculating quantities.
Total Shingles for One Square
Now that we know what a square is and the number of shingles in a bundle, we can estimate the shingles needed for one square of roofing.
The most direct way is to take the total shingles per bundle and divide by 3 squares, since each bundle covers 3 squares:
- 3-tab shingles: 27 shingles per bundle / 3 squares = 9 shingles per square
- Architectural shingles: 36 shingles per bundle / 3 squares = 12 shingles per square
As a formula:
Shingles per Square = (Shingles per Bundle / 3 Squares)
This calculates how many shingles go into one square. For a 3,000 square foot roof, multiply this by the total number of squares to get the requirements.
Examples of Shingles for One Square
Here are some examples of calculating shingles for one square for different shingle types and bundle sizes:
- 3-tab: 22 bundles x 27 shingles = 594 shingles. 594 / 3 squares = 198 shingles per square.
- Architectural: 18 bundles x 36 shingles = 648 shingles. 648 / 3 squares = 216 shingles per square.
- Synthetic slate: 10 bundles x 10 shingles = 100 shingles. 100 / 3 squares = 33 shingles per square.
Adjusting for Roof Pitch and Waste
The pitch, or steepness, of the roof also impacts the number of shingles required. As pitch increases, shingles are cut in more places and material waste goes up. The calculation must factor in this waste.
Typical pitch adjustments are:
- Low pitch roofs (4/12 to 6/12): Add 5% more shingles
- Steep pitch roofs (8/12 or greater): Add 10% more
Additionally, it's smart to account for around 10% overage for material defects and handling waste. Combine the pitch and defect waste factors as needed to determine total extra shingles.
Pitch Multiplication Factors
Here are some common pitch multiplication factors:
- 4/12 pitch: No multiplier needed
- 6/12 pitch: Multiply shingles by 1.05
- 8/12 pitch: Multiply by 1.15
- 12/12 pitch: Multiply by 1.25
Applying the proper pitch multiplier ensures your shingle count provides full coverage on sloped roofs. Steeper pitches require substantially more material.
Shingles for Multiple Squares
For larger roofs, calculate the number of squares needed then multiply by the per-square shingle amount.
Steps for multiple squares:
- Calculate total roof square footage
- Divide footage by 100 to get squares needed
- Multiply squares by shingles per square
- Factor in any pitch adjustment
This gives the estimated total shingles required for full roof coverage. Always round up fractional squares.
Examples for Whole Roof
Some examples:
- 20 square roof x 110 shingles per square = 2,200 shingles
- 35 square roof x 129 shingles per square x 1.15 pitch multiplier = 5,083 shingles
- 47 square roof x 145 shingles per square = 6,815 shingles
Use the same method for any size roof. Accurately determining the number of squares is the key first step.
Once you know the total shingles required, you can estimate cost more reliably and determine how many bundles to order.