How to calculate roof shingles
To calculate the number of bundles of shingles for a gable roof, measure the length and width of the inclined rectangle area and calculate the square footage of the surface area and then double it to get the total footage for the two rectangles of the roof.
Roof rectangle size: 44′ x 16′ = 704 sq. ft.
Total square footage for 2 rectangles = 704 x 2 = 1408 sq. ft
A bundle of shingles has 21 shingles that cover about 32 sq. ft.
1408’/32 = 44 bundles
Along the perimeter of roof (eaves and rakes), shingles (with the tabs facing inwards) are installed as the first layer prior to laying the full courses of shingles. Therefore extra shingles are added on to cover that area. The eaves are located at the lower end of the roof while the rakes are the short ends of roof incline that meet at the peak to form the “V” or gable end of roof.
2 eaves length = 44′ x 2 = 88′
4 rakes length = 16′ x 4 = 64′
Total length of eaves plus rakes = 152 ft
Shingle length = 39 5/16″ or 1 metre.
152′ divided by 3.2760′ = about 47 shingles or 3 bundles.
Calculate the number of ridge caps for Ridge length of 44′.
For every three feet of ridge length; there’s about seven ridge caps, therefore:
44’/3 =14.6 rounded out to 15.
15 x 7 =105 caps, however a shingle has three tabs in it.
105/3 = 35 shingles or about 2 bundles.
Total bundles of roof, rakes, eaves and ridge cap = 44 + 3 + 2 = 49 bundles
Add 5% for waste = 3 bundles
Overall total bundles: 49 + 3 = 52 bundles
One pound of one inch roofing nails will do about three bundles of shingles.
52/3 = 14 lbs of one inch roofing nails. Note: add at least 3 to 5 lbs more nails for waste.
Use one and a half inch nails to secure the ridge cap in place. The ridge caps are made from the shingles by cutting up and along the individual tabs to make three ridge caps.
Have at least a gallon of roofing cement and a one-inch putty knife handy to seal around roof jacks and exposed roofing nails. As well, have at a full sheet of roofing plywood handy in case of plywood roof damage.
A roll of 50 lbs underlayment or similar is required if one is shingling a residential home roof.
Whirly birds and drip edges are optional items for the homeowner to decide upon installation.
To figure out shingles for an intersecting roof or hip roof, divide the surface areas into rectangles and triangles and then calculate the areas of each section to figure out the square footage. Add up all sections to arrive at the overall square footage to figure out the shingle bundles. For the valleys, add at least three extra bundles for overlap.