How to Measure Roof Specs for Your Next Roofing Project

There are several methods for measuring your roof to order roofing materials. Some methods are easier, while other methods yield more accurate results. The method you use might depend on the specific project you’re working on, whether you’re doing it yourself or hiring a contractor, and what type of roof you have. Whatever method you choose, use the step-by-step guide below to take your measurements and perform the necessary calculations.

What tools are needed for roof measurement?

There are different methods for measuring your roof. The exact materials you need will vary depending on what method you use. Here’s a comprehensive list of everything you’ll need to complete the steps in this guide to roof measuring:

• Tape measure
• Level
• Calculator
• Notepad
• Pen or pencil
• Ladder
• Pitch multiplier table (available online)
• Google Earth access (available online)

Method 1: Traditional Roof Measuring

While traditional roof measuring methods provide homeowners with a precise square footage measurement, they can also be dangerous and time-consuming as a DIY project. If you choose to go this route, it may be best to have a professional roofer take measurements for you.

If you’re determined to do it yourself, here are the instructions for the most precise measurements:

Prepare

Gather the necessary materials on your person before climbing the roof. You’ll need a notepad and a writing instrument such as a pen or pencil.

Safety Climb To The Roof

You’ll likely need an extension ladder. To ensure safety, have someone hold the ladder in place while you make the climb. This should not be attempted if you suffer from vertigo or have balance issues. If the worst happens and someone falls from the roof, immediately call 911 or go to the nearest emergency room for evaluation. 

Measure the Outer Perimeter

Using your tape measure, measure the length and width of the roof. This is the only measurement you’ll need if you have a flat roof. If you have a sloped roof, you’ll need additional measurements.

Measure the Slope of the Roof

Using your measuring tape, measure each plane or section of the roof separately.

Measure Other Structures

If your roof has other structures like hip ridges, dormers, or valleys, be sure to measure the length and width of these features as well. These measurements will add to the total square footage.

Check Your Measurements

While you’re on the roof, it’s important to get the most accurate estimate possible for your roofing project. Check behind yourself and ensure you’ve written down your measurements exactly. Don’t round up or down at this stage.

Sketch a Diagram

Make a rough diagram of your roof, including any slopes, hip ridges, or other features. Add your measurements to the diagram.

Divide the Diagram into Simple Sections

Breaking up your diagram into simple roof sections will make calculating measurements for the total sq. feet much easier. Keep going until all sections of the roof have been broken down into squares, rectangles, and triangles.

Make Your Calculations

Calculate the total area of each squared-off section (i.e., squares and rectangles) by multiplying the length times the width. For the triangle sections, multiply half of the base times the height to get the area of each triangle. Record the totals on your diagram.

Total Up the Numbers

Make your final calculation by totaling up the square footage of each section of the roof. This is the total area you’ll use for ordering materials for a new roof. Check yourself a few times to ensure you have the right number. This can save precious time and money as you begin your roofing repairs.

Method 2: How to Measure Your Roof From the Ground

Measuring a roof from the ground may not give you the most accurate results, but it’s a great deal safer and could be a good method to get rough estimates.

Take Measurements of Your House

Using the measuring tape, measure the length and width of the exterior walls of your house. Record these measurements in your notebook.

Calculate the Area of the Roof

To calculate the area of the roof, simply multiply the width and length of your home as measured in the previous step. Write down the total area. Be sure to add rough estimates for any roof overhangs or other features.

Measure the Roof Pitch

To measure the pitch of the roof, you’ll need a ladder high enough to reach it. You don’t need to get on the roof, but you will need to place a level on the roof’s surface a few feet from the edge.

Position the level so that the floating bubble is at the very center. Once you’ve done this, you’ll want to measure the distance between the end of the level and the roof’s surface. Record the results as x:12. So, if your measurement is 3 inches, record it as 3:12.

If your roof isn’t flat, you may need to measure the pitch of other roof features such as dormers, ridges, or Dutch gables, for example.

Use a Pitch Multiplier Table

Perform an online search to find a reliable pitch multiplier table. Plug your numbers in to get the pitch multiplier. Record this number in your notepad.

Calculate Total Square Feet

To get the total square feet of your roof, calculate its total area by the pitch multiplier.

Divide Sq.Ft by 100

Shingles come in packs with enough material to cover 100 square feet of roof. To calculate how many packs you’ll need, simply divide the total square footage of the roof by 100. Roofing contractors often advise ordering 10 percent more materials than you need to make up for the waste factor.

Method 3: How to Measure Your Roof Using Google Earth

If you’re at all tech-savvy, you can measure your roof using Google Earth. Simply type in your address in the search bar and then zoom in as much as possible to view the top view of your house clearly.

Print Out A Top View of Your House

Print the top view of your home from multiple angles.

Use the Ruler Tool to Measure the Roof

Click on the ruler icon to begin measuring the roof. Be sure to change the scale on the ruler to feet. In some cases, you might need to go into settings to change the units of measurement from metric to imperial. Then, just click on the starting and stopping points for each section of your roof and record your measurements on the print-out of your roof.

Make Your Calculations

Use the instructions above to calculate the total square footage of your roof, plugging in your numbers from Google Earth.

This high-tech method of measuring your roof might be the easiest and most convenient way, but it’s also the least accurate. Don’t use this method if you need precise measurements. If you are just looking for a ballpark figure, though, Google Earth might have the answers you need.

Skip The Hassle & Leave it to the Experts

Measuring and calculating roof runs and roof rises isn’t for everyone. If this project seems overwhelming, call in the experts to help you with your roofing project or to answer any questions you might have before getting started.