How to Measure Roof Square

weathered roofing shingles
  • 1-2 hours
  • Intermediate
  • 4000-60000
What You'll Need
Tape measure

Measuring your roof square is an important step when determining how much roofing material you will need during repair or replacement. No matter how large or small your home is, if you have lived in it 15 to 20 years, or plan to, repairing or replacing the roof is inevitable. Your roof is subject to wear from years and years of being exposed to nature's elements. Repairing or replacing your roof is an extensive job so accurately calculating the square footage will get you started on the right foot and avoid wasted time, material, and money.

Step 1 - Understand your Roof Surface

A home's roof is measured in squares. Each square is 100 square feet. If your roof is 5,000 square feet, you will have 50 squares. If you are replacing your entire roof, you will need to purchase shingles in 50 squares to sufficiently cover your 5,000 square foot roof.

Make a sketch of your roof before you go out to measure it. This will better help you understand it when you are measuring and you can write down your measurements onto the sketch. To measure your roof, you will have to understand geometry to a certain extent. The base length multiplied by the height of a triangle is two times the triangle's area. So in order to get the area of the triangle, divide the sum of the base and height by two for the triangles true area. It is a good idea to add 10 percent to each of your measurements to compensate for trimming and waste.

Step 2 - Section the Roof


If you have a roof that has different dimensions such as gable ends and hip ends, the sketch of the roof you've drawn up will come in handy. You will have to measure your roof in sections and record it on the sketch. This makes measuring simpler and easy to keep up with your total numbers when purchasing squares of shingles.

Step 3 - Consider the Roof Slope

To determine the slope of your roof, you will have to know the slope of your deck. In order to calculate this, measure the vertical rise of your deck over a 12 inch horizontal distance in inches. For instance, if the measurement is four inches over the 12 inch horizontal distance, your roof slope will be 4/12. When presenting your roof slope, the vertical rise is always before the horizontal run.

Step 4 - Take Ground Measurements

blueprints, tape measure, and calculator

Depending upon what type of roof your home is outfitted with, measurements can be taken from the ground. This means, you can take measurements of your home's perimeter to determine the square footage. For example, if your home is 60 feet long and 40 feet wide, you would multiply the length by the width and come up with 2,400 square feet. This number will provide you the level area beneath the roof. To convert the square footage to roof squares, divide the square footage by 100. The roof surface area would be 24.

If you use ground measurements to determine your roof squares, you will need to also compensate roof overhang and slopes to get an accurate count. Use the instructions for obtaining roof slope to add to your ground measurements.