How To Measure A Roof Quickly and Accurately


Construction jobs that are focused on roof repair and replacement can be a daunting task. Not only is it costly and dangerous, but a roof consists of many challenging angles and dimensions. So, one of the most important considerations in both design and construction is being able to measure a roof accurately, and also in a timely fashion.

There are a few proven ways to measure a roof, some through technology, others by a hands on approach. If you trust yourself on a roof, the most accurate measurements come from being able to take a tape measure and measure these spots for the greatest accuracy. Additionally, you could also depend on satellite roof measurement, which involves taking imagery from a maps service that shows a sky view and can measure through the imagery. These are the two most effective ways to measure.

Hands on Approach

As always, make sure you can safely get onto the roof. If the pitch is too high on your roof, you may either need a professional to get on the roof to measure or you may want to utilize a satellite roof measurement. When you get on top of the roof, make sure you can access all parts of the roof. You will want to start by measuring the width of each side of the roof that goes from the bottom to the apex of the plane.

Next you will want to measure the full length of the roof plane. If your roof has hip ridges, valleys, or dormers, just measure the length of the roof across the apex. Then go on to measure the length and width of your hip ridges, valleys, or dormers. A good tolerance of accuracy should be to the nearest 1/2 inch. It is important to keep your tape measure as straight as possible as any slack in the tape will skew your results. If possible, have a partner help you when measuring long lengths to keep one end of the tape intact.

In most cases, a roof should be asymmetric. But to be safe always measure both sides especially if you do not know for sure if each plane of a roof is a different pitch. It is more commonplace now with extensions to see a roof with non-symmetric pitches.

Finally, when you get all your measurements together, you will want to begin to draw out what you’ve measured. Start with a two dimensional sky view of the roof and just start labeling all the edges of your drawing as you measured it on the roof. It is important that you measure every edge of a roof plane and any hip ridges, valleys, or dormers. So, make sure if you missed any, play it safe and measure it instead of guessing.

To determine the roof pitch, measure the width of your house. When you add together the width of each main roof plane, it should be much greater than the width of your house. Since most roof planes make a right triangle, basic trigonometry should help you determine the pitch angle and the height of the apex. You can use an online pitch multiplier tool if you need assistance. This is only important if you need to replace the entire roof.

When it comes to materials particularly with re-shingling, you should first add up all the square footage you calculated from the measurements. If you do not have any hip ridges, valleys, or dormers, the calculations should be straight forward as they will be just two rectangular sections. If you do have these features, you will have to do some more complicated math to get to the final calculation. Your final number should be a square footage. Most shingle materials come in packages called squares which translate to approximately 100 square feet. The total square feet of your roof divided by 100 is the total number of packs of shingles you will need to buy. Always add 10 percent to this final calculation for potential mistakes and waste.

Satellite Roof Measurement

As an alternative to a hands on approach for determining materials, you could utilize existing technology. Satellite imagery is available for free on most map based websites and allows you to see a satellite view in high resolution, and able to zoom to a scale that allows you to see your roof. On top of that, most of these mapping websites have built in tools that allow you to instantly measure on the web interface at the scale you are observing.

Using this technology, you can easily obtain a view of the outer perimeter of your roof. You would start by measuring the length and width. The only setback to this technology is that it is a 2d representation and does not reflect pitch, meaning whatever the width of your roof shows would be an underestimate. You can easily adjust for this by learning what your pitch is and using a multiplier on the width, to get total area.

Similar to measuring by hand, you will have to factor in adjustments due to hip ridges, valleys, or dormers. Luckily, with today’s high resolution and colored satellite views, it is quite easy to spot the outlines with the map view of where the hip ridges, valleys, or dormers start and end. Again, you will need to know the pitch of these pieces so that you can use a multiplier against the width to determine true square footage of your roof.


Measuring your roof is always one of the first steps you must make when you are getting ready to undergo shingles replacement and/or structural repairs. If you make accurate measurements and measure every key length and width the first time, the process should be quite simple and quick. Always consider a multiplier for pitch, and always add 10 percent to material based on your measurements. Usually once the measuring is done, you should not be too far away from starting construction on your roof replacement project.