How to Calculate Roofing Square Footage [And 5 Popular Roof Types]

Roofing Square footage infographic

Replacing a roof is likely something every homeowner dreads. But when it comes time to replace it, it’s important to be prepared.

Understanding how to calculate roofing square footage is an important step when it comes to planning a roofing project or obtaining a quote from a contractor. The square footage of the roof will determine how much material is needed and how much the project will cost. 

In this blog post, we’ll explain how to measure and calculate the square footage of your roof so you can accurately estimate the cost of your roofing project. Whether you’re planning to replace an old roof or install a new one, understanding the square footage of your roof is an essential part of the process.

Calculating Roof Square Footage

To calculate your roof’s square footage, you’ll need to measure the length and width of the roof and multiply those numbers together to find the total area. 

For example, if the length of the roof is 40 feet and the width is 20 feet, the total area would be 40 x 20 = 800 square feet.

Here’s an example of calculating the roof square footage:

  1. Measure the length of the roof: Let’s say the length of the roof is 40 feet.
  2. Measure the width of the roof: Let’s say the width of the roof is 20 feet.
  3. Multiply the length and width: 40 x 20 = 800 square feet.
  4. Calculate the roof square footage: The roof square footage is 800 square feet.

It’s important to measure the roof accurately to get an accurate calculation of the square footage. 

Slope & Complexity 

The slope of a roof is the angle at which it sits in relation to the ground. It is typically expressed as a ratio, such as 4:12 or 6:12, which represents the number of inches the roof rises for every 12 inches it runs horizontally. A roof with a slope of 4:12, for example, rises 4 inches for every 12 inches it runs horizontally.

The complexity of a roof refers to the number and shape of the planes that make up the roof. A simple roof has a single plane, while a more complex roof may have multiple planes and a variety of slopes and angles. A complex roof may be more difficult and expensive to install and maintain, but it can also add visual interest and character to a home.

The slope and complexity of a roof can affect its performance and durability. A steep roof may be more resistant to wind and water damage, for example, while a flat roof may be more prone to leaks and ponding water. A complex roof may require more maintenance, such as regular cleaning and repairs, to keep it in good condition.

It can be helpful to draw a sketch of the roof and mark the measurements on the sketch to make sure you have the correct measurements. You may need to measure multiple sections of the roof and add up the total square footage if the roof has multiple planes or areas with different slopes.

Cost Factors 

There are several factors that can affect the cost of replacing a roof:

Size of the Roof 

The cost of the roof will depend on the size of the roof, which is typically measured in squares (100 square feet). The larger the roof, the more materials and labor will be required, which will increase the cost.

Type of Roofing Material

Different roofing materials have different costs. Asphalt shingles are usually the least expensive option, while tile, metal, and wood can be more expensive. The cost of the roofing material will depend on the quality of the material and the price of the material in your area.

Roof Slope

The slope of the roof can also affect the cost of the replacement. A steep roof may be more difficult and time-consuming to work on, which can increase the cost.

Complexity of the Roof

A more complex roof with multiple planes and angles may be more expensive to replace than a simple roof with a single plane.

Removal of the Old Roof

The cost of removing the old roof and disposing of the materials will also be included in the total cost of the replacement.

Local Labor Rates

The cost of labor can vary depending on where you live. In some areas, labor costs may be higher due to a higher cost of living.

It’s a good idea to get estimates from several contractors to understand the cost of replacing your roof. Be sure to compare the estimates based on the same materials and scope of work to ensure an accurate comparison.

Other Factors to Consider 

Infographic with person holding a ruler to calculate roofing square footage

There are several factors to consider when choosing a roof type for your home:

  • Climate: Different roof types are better suited for different climates. For example, a flat roof is more common in dry, hot climates, while a pitched roof is better for wet, cold climates.
  • Material: Different roof types are made from different materials, such as asphalt shingles, metal, wood, or tile. Consider the availability and cost of the materials in your area, as well as their durability and maintenance requirements.
  • Style: The roof should complement the style and architecture of the home. A colonial-style home, for example, would look out of place with a modern flat roof.
  • Energy efficiency: Some roof types are more energy efficient than others. A white or light-colored roof, for example, can reflect sunlight and help reduce the heat gain in your home, which can lower your energy bills.

It’s a good idea to consult with a roofing contractor to discuss your options and get an estimate for the cost of the roof. They can also help you assess the condition of your current roof and recommend any necessary repairs or replacements.

Popular Roof Types 

As for popular roof types, there are many different types of roofs to choose from, each with its own unique characteristics and advantages. Some of the most popular roof types include:

Asphalt Shingle Roofs

Asphalt shingle roofs are made of asphalt shingles that are attached to the roof using nails or adhesive. These roofs tend to be the most inexpensive and easiest to install, making them a popular choice for many homeowners.


  • Inexpensive 
  • Easy to install 
  • Available in a wide range of colors and styles


  • Short Lifespan 
  • Vulnerable to wind damage 
  • Difficult to dispose of 

Metal Roofs

Metal roofs are made of metal panels that are attached to the roof using screws or other fasteners. These roofs are durable and long-lasting, and they can be made from a variety of different materials, including aluminum, steel, and copper.


  • Durable and long-lasting 
  • Can last for up to 50 years or more
  • Resistant to fire, wind, and hail


  • Expensive 
  • Much louder than other roof types 
  • Expand and contract with drastic temperature changes
  • Can dent by hail, branches, etc. 
  • More prone to lightning damage 
  • More prone to ice dam formation, which can cause leaks 

Tile Roofs

Tile roofs are made of concrete or clay tiles that are attached to the roof using nails or adhesive. These roofs are known for their durability and longevity, and they are often used on Spanish-style or Mediterranean-style homes.


  • Extremely durable 
  • Can last for up to 100 years or more
  • Low maintenance, requiring only occasional cleaning


  • Expensive 
  • Very heavy – could require additional structural support
  • Fragile 
  • Repair is time-consuming and labor-intensive
  • Require more maintenance
  • Not suitable for all climates 

Flat Roofs 

Flat roofs are just what they sound like – flat, rather than sloped like most roofs. These roofs are common on commercial buildings and some residential buildings, and they can be made of a variety of materials, including asphalt, rubber, and PVC.


  • Easy to install and maintain
  • Less expensive than other types of roofs
  • Good choice for homes with a modern or contemporary design


  • Prone to water pooling 
  • Have certain weight limits 
  • Require regular maintenance 
  • Not suitable for all climates 
  • Shorter lifespan 

Green Roofs 

Green roofs, sometimes called living roofs, are roofs that are covered with vegetation, such as grass, plants, and shrubs. These roofs are environmentally friendly and can help to reduce energy costs and improve air quality.


  • Reduce energy costs 
  • Provide insulation and cool the air around the home
  • Help to improve air quality 
  • Provide a habitat for wildlife


  • Expensive 
  • Very heavy – require a layer of soil and vegetation on top 
  • Require regular maintenance 
  • Not suitable for all climates 
  • Shorter lifespan
  • Water pooling 
  • Not super accessible 

Overall, the type of roof you choose will depend on your personal preferences, the style of your home, and your budget. Consult with a roofing professional to determine the best roofing option for your needs.

How Long Does Your Roof Last?

The frequency of replacing your roof will depend on a variety of factors, including the type of roof you have, the age of your roof, and the climate you live in. In general, most roofs will need to be replaced after about 20 to 25 years, although some types of roofs may last longer. 

For example, a metal roof can last for up to 50 years, while a tile roof can last for up to 100 years.

To determine the age of your roof, you can check the manufacturer’s warranty or consult with a roofing professional. It is also a good idea to inspect your roof regularly for signs of damage or wear, such as missing or damaged shingles, leaks, or water damage. If you notice any of these signs, it may be time to replace your roof.

In general, it is a good idea to replace your roof before it reaches the end of its lifespan, as this can help to prevent more serious damage to your home. If you are unsure about the age or condition of your roof, it is a good idea to consult with a roofing professional to determine the best course of action.

How to Keep Your Roof In Good Shape

There are several steps you can take to protect your roof and extend its lifespan. Some of the most effective ways to protect your roof include:

Perform Regular Maintenance 

Regular maintenance is key to protecting your roof. This includes inspecting your roof regularly for signs of damage or wear and addressing any problems or issues as soon as they arise.

Keep it Clean

Cleaning your roof can help to prevent the build-up of debris, such as leaves and branches, which can cause damage to your roofing materials.

Repair Any Damage

If you notice any damage to your roof, it is important to repair it as soon as possible. This can help to prevent more serious damage and extend the lifespan of your roof.

Choose the Right Materials

The type of roofing materials you choose can have a big impact on the lifespan of your roof. Choose high-quality, durable materials that are designed to withstand the weather and climate in your area.

Consider a Roofing System 

A roofing system is a combination of materials and techniques that work together to protect your roof. This can include things like underlayment, ventilation, and other elements that help to keep your roof in good condition.

Overall, protecting your roof is an important part of maintaining your home and keeping it in good condition. By following these tips and working with a professional roofing contractor, you can help to extend the lifespan of your roof and prevent more serious damage.

We know replacing your roof isn’t fun, but understanding how to calculate your roofing square footage can help you make informed decisions for your family. 

It is always a good idea to consult with a roofing professional to determine the best roofing materials and techniques for your specific climate. 

You might also be interested in: 10 Roofing Materials Every Homeowner Should Consider

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