How To Accurately Measure a Roof From the Ground

An Introduction to a Simpler Method

What I’m about to share with you is one of the best-kept secrets for measuring residential roofing jobs without your feet leaving the ground. If you are not the owner of a residential roofing company, you most likely haven’t heard of this before. This was taught to me several years ago by one of my roofing subcontractors. It is a super-simple, highly accurate, and safe way to quickly measure the size of just about any style of asphalt shingle roof.

The "Shingle Count" Method for Rectangular Sections

To sum it up, each individual tab on a 3-tab shingle measures approximately 12 inches wide by 6 inches high. The process is as follows:

1. Begin by counting the number of shingles from left to right; this gives you the total width of the section in feet.
2. Next, count the number of rows of shingles between the gutter and the peak of the roof and then divide that number by two; this gives you the height measurement.
3. Simply multiply the width and height together, and the result is the total square feet of that particular section.
4. Proceed to do the same thing for each of the remaining sections.

Handling Triangular Sections

When I encounter any triangular-shaped roof sections such as dormers, I count the shingles from side to side where it is widest and then count the shingles from the gutter to the peak. Since these triangular sections are only a small percentage of the entire roof, I just use the resulting number even though it is slightly larger than the actual area.

The Technique for Estimating Hip Roofs

There is a different technique I use when measuring "hip" roofs, which have four sides and are shaped kind of like a pyramid. These roofs make it tough to count shingles, so through trial and error, I came up with a little calculation that has provided me with another simple but accurate estimation. When using this second calculation, the total square footage you end up with may be a little higher than what is actually there. But I would rather slightly overestimate the size of a roof job than underestimate it.

For Hip Roofs, I measure the length of the house and then I measure the width. I then multiply these two numbers together and take that number and multiply it by 1.35.

Test Before You Trust

Please don’t blindly use these methods without testing them out first. On your next roofing estimate, I suggest that you compare the total square footage number you get by actually measuring a roof to the number you end up with after using these two little calculations. Once you see how surprisingly close the end result numbers are to each other, you can then decide whether or not to retire your ladder with confidence.

I hope you find this info to be as time-saving and helpful as I have.