How to Calculate a Roofing Square

Roofing shingles sell by the square.
One square of roofing material is equal to 100 square feet, or a perfect square shape that is 10-by-10. Roofing shingles are individually packaged in bundles. Each bundle is equal to 33 1/3 square feet. Three bundles of shingles is equal to one square of roofing, or 100 square feet. Calculating your roof’s square area will mean having to climb on the roof.

Step 1

Set the extension ladder against the side of the home. Follow all safety directions printed on the side of the ladder. Climb the ladder to the roof.

Step 2

Measure the overall length of the roof with the tape measure.

Step 3

Run the tape measure from the lower end of the roof up to the middle of the upper peak. This is the width of the roof.

Step 4

Multiply the length times the width. The result is the square footage of the roof for that area. Perform the same measurements and calculations for all areas of the roof.

Step 5

Add all of the square footage calculations together. Divide that total by 100 square feet. The result is equal to the number of squares required to cover the roof.

Step 6

Divide the number of squares by three. The result is the total number of shingle bundles that is needed for covering the roof.

Things You Will Need

  • Extension ladder
  • Tape measure


  • You may wish to add in one extra square for any miscuts, valley shingles and shingles needed for covering the peak. The peak on any roof is where two opposite sides of a roof come together. The exposed joint between the mating shingles must be covered with a layer of single-cut shingles.
  • If you are hesitant about climbing on your roof, contact a roofing contractor to perform the measurements for you.