How to Measure a Roof for Shingles

Measuring a roof for shingles might sound like a daunting task, but don’t worry. It’s not as complicated as it seems. With a few simple tools and some basic math skills, you can measure your roof like a pro.

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Are you planning to install new shingles on your roof? Before you start, it's crucial to measure your roof accurately to ensure you buy the right amount of shingles. If you don't measure correctly, you could end up wasting time, money, and materials. In this article, we'll guide you through the process step-by-step, so you know exactly how to measure your roof for shingles prior to a new roof installation.

How to Measure a Roof for Shingles 

Measuring the roof in order to have the number of shingles needed is most important when installing a new roof or repairing an existing one. It's easy to end up spending more money than is necessary when you purchase too many or too few shingles. If you are a do-it-yourself person and you want to tackle roof repairs or even a replacement, you need to properly measure your roof.

Roofer on roof showing how to measure roof for shingles

What You Need To Measure Roof For Shingles

When measuring the roof, you will need the tools for the job. A roof square footage calculator, roofing square calculator, or shingle calculator can help. But, you really need to know how to measure to ensure the measurements you enter into the calculators are correct in order to purchase the right number of shingles.

Why Accurate Measurement Is Important

Calculating your roof's total square footage precisely is important for setting your budget and determining the amount of material you need. The cost of roof shingles, metal roofs, and other materials is mainly determined by square footage. The more accurate your measurement, the better you can plan. If you purchase too many materials, you waste money. If you purchase too few materials, you waste time by needing to acquire more.

Preparing the Site for Measuring

Choose a day with a favorable weather forecast to do your measurements and set up your ladder in accordance with proper safety practices. You will need measuring tape to acquire roof length and height. Once on the roof, pay attention to your surroundings to avoid slipping. You may want to invest in a safety harness, which is purchased as part of a fall prevention kit that also includes ropes and fasteners.

The best first step is to draw a basic diagram of your roof so you don't forget any surfaces. The diagram doesn't need to be drawn to scale, but it does need to include all the roof's features that affect the number of necessary shingles. Remember you'll also need to measure surfaces without shingles, such as chimneys, and subtract them from the total area.

How to Measure Your Roof Square Footage

Marking the Perimeter of Your Roof Area

First mark the perimeter of your roof area so you can see the sides of the roof. You will need to find the total square footage of the roof.

  1. Measure the length and width of each plane on the roof, including dormers. Then multiply the length by the width.
  2. Add the square footage of each of the planes together.

Using a Tape Measure to Calculate the Lengths of Each Side of The Roof Plane

Walk up to the peak of the roof to get an idea of the layout and make sure to orient the overhead sketch in the notepad to your current position. This will help ensure that you're labeling each plane accurately. Choose the first section of the roof to be measured and lay your measuring tape out along the length of the plane. Write down the first measurement in the corresponding location in your notepad, then lay the tape out along the width of the plane to find the corresponding measurement.

If you are measuring from the peak of the roof (perpendicular to the peak), you will need to stand on one side of the roof and feed the measuring tape down to the bottom edge. Measure from the edge to the exact peak and record the measurements.

If you are measuring along the peak (parallel with the peak), place the tape measure at the edge of the roof on one side of the peak and run it across to the other edge of the plane along the peak.

Repeat the process of measuring both the length and width of each roof plane, then climb down from the roof using the ladder (with a partner holding it steady). Use these measurements to calculate the square footage of each plane. Keep in mind that some roof planes may not be square or rectangular. Common alternatives are trapezoids and triangles. The formulas for calculating the surface area of rectangles, squares, trapezoids, and triangles are listed below.

Area of a rectangle or square: A = L x W Area = Length x Width Example: 20 feet x 10 feet = 200 square feet

rectangle area formula for determining the area of a roof

Determining The Pitch Of Your Roof

Roof pitch, as well as the roof area, is a determining factor for the cost of the roof and the type of materials used. It affects walkability as well as drainage, and roofs in areas of high rain or snowfall tend to have steeper pitches.

Roof pitch is the measurement of a roof's vertical rise divided by its horizontal run. It is often compared to slope, but is not exactly the same. In the United States, a run of 12 inches (1 foot) is used, and pitch is measured as the rise of the roof over 12 inches. For instance, a 7:12 roof pitch means that the roof rises 7 inches for every 12 horizontal inches. Outside of the U.S., a degree angle is typically used.

In other words, you would measure the height from the roof or rafter to the level 12 inches away from where it meets the surface. This measurement will be your rise. This measurement is shown as a ratio of rise over run. For example, if your roof rises 4 inches over a run of 12 inches, then it has a roof pitch of 4:12. 

Estimating the Pitch Of A Gable or Hip Roof with a Carpenter's Level and Tape Measure

You can estimate the pitch of a gable or hip roof using a carpenter's level and tape measure several different ways. Take a tape measure and a level up to the attic. 

From the Top of the Roof

  1. Use a ladder and fall protection equipment when going onto the roof.
  2. Bring a level and a tape measure or ruler to the roof. The level must be at least 12 inches long.
  3. Hold the level perfectly flat so one end touches the roofing surface.
  4. Measure the vertical distance (up) from the roof surface to the level's 12-inch mark. The number of vertical inches is the rise. For example, if you measure a 4-inch distance to the level it means the roof rises 4 vertical inches for a 12-inch horizontal run for a pitch of 4/12.
  5. Using a combination square can make it easier to keep the tool level while making and recording the measurements.

From Inside the Attic

  1. Bring a tape measure and level to the attic.
  2. Hold a 12-inch level so that one end touches the sheathing. Make sure the level is perfectly straight. It is easier to do when the level can rest on the top of a ceiling joist.
  3. If you can hold the level alongside a rafter, clamp the level in place.
  4. Measure the vertical distance (up) from the level's 12-inch mark to the roof. The number of vertical inches is the rise. The roof pitch is the rise divided by the run.

Calculating the Pitch of a Flat or Low Slope Roof with an Angle Finder Tool

You can use an angle finder tool when your house has a low-slope roof. If it has a flat roof, there is no pitch, so you need to express the pitch of a flat roof by using 0 or 0/12. The angle finder tells you the pitch of the roof when you put it against a straight angle.

A low slope roof can look like a flat roof but there is a slop, even though the slope is slight and gradual. The lowest slope of a roof is 1/12. These type of roofs are often on back patio porches or at the top of an older gambrel roof. A roof that is 2/12 is a bit steeper than 1/12.

Calculating Material Requirements Based on Pitch and Square Footage

The amount of materials you need is dependent on the pitch and square footage of the roof.

Converting Square Feet Into “Roof Squares” (100 Square Feet) For Low Slope & Flat Roofs

Roof surfaces are measured in "squares." A roofing square is equal to 100 square feet of the roof. To determine the number of squares on a gable roof, divide the total square feet by 100. For example, if the roof is 2,400 square feet, divide 2400 by 100 for a total of 24. This roof would be 24 squares and you would need that number of squares of shingles to cover it. Add 10% - 15% to all your material totals for trim allowance (waste factor).

Utilizing A Roofing Calculator To Determine Bundle Quantities For Steep Slope Shingle Projects

A roofing calculator will help you calculate the number of shingle bundles that are required for your roof project, especially if you have steep slopes. Each bundle of shingles has between 15 and 29 shingles. A bundle usually covers 33 square feet regardless of the shingle type. To measure using a roofing calculator, first, you enter the dimensions as you measure them from the ground, for example, length, width, and roof pitch. The calculator then gives an estimate of shingle bundles and the synthetic or felt underlayment material that you will need.

How To Choose The Best Materials For Your Project

Now that you have the measurements and have calculated how much of the materials you need, it's time to select the best materials to use for your project.

Asphalt Shingles – Types, Warranties, Cost & Durability

Asphalt shingles are the most popular residential roofing option in North America. They are made to be durable, with some shingles lasting decades while requiring minimal upkeep. 

Types

Strip Shingles:

Strip shingles are also called three-tab shingles and are the most basic and affordable type of asphalt shingle. They are named for the cut of the shingle and come in the form of a single, flat layer of asphalt.

Dimensional Shingles:

Dimensional shingles, also known as architectural or laminate shingles, are the most prevalent roofing choice in the United States. They are made from two or more laminated layers of asphalt to create a multi-dimensional look that replicates the appearance of natural wood shake roofing or slate tile roofing.

Luxury Shingles:

Luxury shingles are high-end laminate shingles. They provide greater protection from the elements, deeper quality of color blends and gradations, and sophisticated designs that add value and beauty to the exterior of your house.

Different types of laminate shingles displayed

Warranties

Each manufacturer offers warranties on the type of shingle. Usually, a warranty is 25 to 30 years of coverage for asphalt shingles. Some other warranties may last for 50 years or a 50-year, depending on the brand of shingle and the company that produces it. For example, most architectural shingles carry a 50-year or 50-year-limited warranty against manufacturing defects. Our work is covered by the Owens Corning Platinum Protection Warranty, one of the best warranties available.

Costs

Costs for shingles vary based on the type of shingle. Here are some ranges for different types of shingles. Check out our pricing page for a more in-depth look at roof pricing.

Shingle MaterialTotal Price per Square Foot
Architectural asphalt shingles$4.50 - $12.25
Basic asphalt shingles$4.25 - $8.25
Composite shingles$7.50 - $13.00
Slate shingles$12.00 - $22.00

Other Popular Options – Metal, EPDM Rubber, Tile & Wood Shake/Shingle

There are quite a few other popular shingles besides asphalt. Metal and steel roofing is the fastest growing material in roofing today. There are options that look like other types of shingles. Metal is durable and lasts up to 60 years or more, standing up to all weather conditions. It is more expensive than asphalt, but given the long life it can be very cost effective.

EPDM is an extremely durable synthetic rubber roofing membrane that is widely used in low-slope buildings in the U.S. and the world. EPDM is one of the best choices for a flat or low-slope roof. It is one of the least expensive to install and repair as well as being durable, long-lasting, and lightweight.

Tile shingles and slate shingles are sometimes grouped together as a type of roofing shingle. The fundamental distinction is that slate roofing is a natural stone while tiles are a manufactured product. Generally, tile roofing is a cheaper alternative to slate tiles. Installation of both types requires expertise and is labor-intensive. 

Wood shakes and shingles, though very similar, are different. Wood shingles have a smooth and uniform look while wood shakes are traditionally hand split giving them a rougher texture and finish. So, wood shakes lack uniformity across each shake and the entire roof. Wooden shakes cost more than shingles because it costs more to manufacture the shakes. You can estimate that a wood shake or shingle roof will last around 30 years if it is properly installed and maintained.

Installation Considerations

Each type of shingle is installed differently. However, there are five things you should consider when you are replacing your roof.

1. Choose to fully replace your roof instead of nailing over shingles to reroof. If you reroof, you won't qualify for an enhanced warranty. Your roof shingle may look different than the old one and it's harder to repair a roof leak.

2. Determine your roof replacement budget. If you have a budget of $12,000 to $15,000, you should look at asphalt shingles. If you want to upgrade to a luxury asphalt shingle, you should expect the price to double. A standing seam metal roof will be 3 times the price of an architectural shingle.

3. Choosing the right roofing material.  Think about how long you want the roof to last, what has the best material warranties, and how important curb appeal is to you.

Hiring A Professional Roofer

If you have decided that the roofing job is too much for you to do yourself, you are then faced with hiring a professional roofing company to do the work. Here are important things you should know before hiring a roofing contractor.

Things To Look For When Choosing A Professional Roofer

Here are seven tips for hiring a professional roofing contractor:

  1. Look for a license.
  2. Check if they have insurance and are bonded.
  3. Determine how much experience they have.
  4. Check to see if they are local.
  5. Check their contract.
  6. Request price estimates.
  7. Think about your needs.

Questions To Ask Potential Contractors Before Hiring Them

  • How long have you been in business?
  • How local is your business?
  • Who owns your business and how long have they owned it?
  • What jobs have you done that I can go see?
  • Who will be installing my roof?
  • Can you tell me about your insurance?
  • Do you have the appropriate license to do the work?
  • Do you have a warranty on your work?
  • Do you use roofing subcontractors?
  • Do you provide a written estimate?
  • How will you protect my lawn?
  • What do you do to ensure the project is on time?
  • What do you do with refuse material?

Contact Allied Roofing Solutions for Your Roof Replacement

If you want the job done correctly, call Allied Roofing Solutions. Our team of professionals can guide you and give you all the information you need to make the best decision on your roof replacement. Whether you need a roof repair or replacement, we will provide a premium level of service. Call us at  (201) 773-0633 or complete the free estimate form to schedule an appointment.