Getting your shingle calculations right is crucial for any roofing project. Estimating incorrectly can lead to costly over-ordering or, worse, running out of shingles mid-project, causing delays and potential damage.
This article serves as your go-to guide for understanding and figuring out exactly how many shingles you’ll need. We’ll cover everything from roofing squares and shingle bundles to calculation methods and all the factors that can influence how many shingles you ultimately require. You’ll know how many shingles in a square you will need to complete your project.
Understanding roofing measurements: squares and bundles
When you’re shopping for shingles, you’ll run into terms like “square” and “bundle.” Here’s what those terms mean.
What is a roofing square?
A roofing square is a unit of measurement equal to 100 square feet. Roofers don’t measure a roof in feet; they measure it in squares.
Why? It’s just more convenient. Imagine calling a roofer and telling them you need enough shingles to cover 1,850 square feet. It’s much easier to say you need 18.5 squares of shingles.
What is a bundle of shingles?
Shingles are packaged in bundles, which makes them easier to carry and transport. The number of shingles in each bundle may vary based on the type of shingle, but a bundle will typically cover about 33 square feet — roughly a third of a square.
Shingle count by type
The number of shingles you’ll need per square will depend on the type of shingle you choose.
Asphalt shingles
Standard three-tab asphalt shingles usually come in bundles of around 29 shingles each. With a 5-inch exposure, you’ll typically need about three bundles per square.
Standard asphalt shingles usually come in bundles of 21 to 23 shingles.
Architectural shingles
Because architectural shingles are larger than standard shingles, you’ll need about four bundles per square. Each bundle typically contains around 21 shingles, although some may contain as few as 15 or as many as 22.
Wood shingles
Wood shingles typically come in bundles of approximately 25 shingles.
Factors affecting bundle count
As you calculate how much roofing material you’ll need, keep in mind that the following factors can affect the number of shingle bundles required to cover your roof:
Roof pitch
The pitch of your roof will affect the quantity of shingles you need to buy. Steeper roofs require more shingles than flatter ones. To get the most accurate estimate, you may want to use slope correction factors, available from roofing suppliers or online calculators.
Roof complexity
The more complex your roof design, the more shingles you’ll need. Roof features like dormers, skylights, and valleys will all increase the amount of shingles you’ll need to purchase to complete the job.
Shingle exposure
Shingle exposure refers to how much of each shingle is exposed to the elements. With standard three-tab asphalt shingles, the typical exposure is 5 inches. If you’re using a different type of shingle, be sure to adjust your calculations accordingly.
Calculating the number of bundles needed
Once you know how many shingles you’ll need to cover a square, you can use that knowledge to figure out how many bundles to buy.
Step 1: Measure the roof area
You’ll need to measure the length and width of each plane of the roof. You can use a tape measure for this, but if you don’t like heights, you can use architectural drawings or even satellite images to get the measurements you need.
Step 2: Convert to roofing squares
Add up the square footage for each plane of the roof to get the total square footage. Then, divide the total square footage by 100 to convert the area into roofing squares. For example, if your roof’s total square footage is 1,700 square feet, you’ll need 17 roofing squares.
Step 3: Determine the number of bundles
Multiply the number of squares by the number of bundles you need per square. For example, if you’re using asphalt shingles, you’ll need three bundles per square. So, for a 17-square roof, you’ll need 51 bundles.
It’s always wise to buy a little extra in case you make a mistake or have some damaged shingles. Most professionals recommend adding 10% to 15% to the total to account for waste.
Don’t forget these other materials!
When you’re estimating roofing materials, remember that you’ll need to calculate extra materials for the eaves, valleys, and ridges of your roof. These areas don’t factor into the square footage of the roof’s surface, so you’ll need to measure them separately.
You’ll also need to figure out how much underlayment you need. Underlayment is measured by the square footage of your roof, so that part is usually pretty simple.
Finally, don’t underestimate the importance of roofing nails! The type and length of nail you need depends on the kind of shingles you’re using, as well as the average wind conditions in your area. Using the wrong nails can lead to leaks and blow-offs, so double-check those specs!
Common Mistakes and How to Avoid Them
Estimating roofing materials can be tricky. Here are a few things people often get wrong:
- Inaccurate Measurements: This is the big one. Don’t eyeball it! Precise measurements are essential for any roofing project. Double-check everything and maybe even get a second opinion if you’re unsure.
- Forgetting About Overlap: Shingles aren’t laid edge-to-edge. You have to factor in the overlap, or you’ll come up short. Check the manufacturer’s specs for the recommended exposure and use that to calculate how much of each shingle is actually covering the roof.
- Ignoring Roof Features: Dormers, skylights, chimneys…they all impact the amount of shingles you’ll need. Take careful measurements around these features and add extra material for cutting and fitting. It’s always better to have a little too much than not enough.
In Summary
Calculating how many shingles you’ll need for your roofing project involves figuring out your roof’s square footage, dividing by 100 to get the number of squares, and then multiplying by the number of shingle bundles needed per square (usually 3).
Getting this calculation right is crucial to avoid wasting money on excess materials or, worse, running short before the job is done.
If you’re tackling a complicated roofing project, or if you’re just not sure about any of these steps, don’t hesitate to get advice from a professional roofing contractor. They can ensure you have the right amount of shingles for a secure, long-lasting roof.