Roofing calculator: how many squares and bundles of shingles?
Enter the footprint (with overhangs) and the pitch. The calculator applies the pitch factor, converts to roofing squares (100 sq ft), adds waste and works out shingle bundles, underlayment rolls and ridge cap.
Price this job as an estimate in Quotesprig (free)
Common sizes, worked out
6/12 pitch, 10% waste, 3 bundles per square, ridge length equal to the footprint length. Every number below comes from the same calculator code as the tool above.
| Job | Pitch factor | Roof area | Squares (with waste) | Shingle bundles | Underlayment | Ridge cap | Labour |
|---|---|---|---|---|---|---|---|
| 30 × 20 ft footprint | 1.118 × | 670.8 sq ft | 7.38 sq | 23 bundles | 2 rolls | 1 bundle | 18.4 hr |
| 40 × 30 ft footprint | 1.118 × | 1,341.6 sq ft | 14.76 sq | 45 bundles | 4 rolls | 2 bundles | 36.9 hr |
| 50 × 30 ft footprint | 1.118 × | 1,677.1 sq ft | 18.45 sq | 56 bundles | 5 rolls | 2 bundles | 46.1 hr |
| 60 × 40 ft footprint | 1.118 × | 2,683.3 sq ft | 29.52 sq | 89 bundles | 7 rolls | 2 bundles | 73.8 hr |
| 40 × 30 ft at 9/12 pitch | 1.25 × | 1,500 sq ft | 16.5 sq | 50 bundles | 4 rolls | 2 bundles | 41.3 hr |
Assumptions you can change
Starting values: waste allowance 10 %, bundles per square 3 bundles, underlayment per roll 400 sq ft, ridge cap per bundle 33 ft, hours per square 2.5 hr. They are typical starting points, not rules: use the numbers on your product labels and your own production rate.
FAQ
How many squares is a 40x30 roof?
For a 40 × 30 ft footprint (6/12 pitch, 10% waste, 3 bundles per square, ridge length equal to the footprint length): pitch factor 1.118 ×; roof area 1,341.6 sq ft; squares (with waste) 14.76 sq; shingle bundles 45 bundles; underlayment 4 rolls; ridge cap 2 bundles. Change any input above for your own job.
What is a roofing square?
One roofing square covers 100 square feet of roof surface (9.29 m²). Shingles are usually sold so that three bundles cover one square; check the wrapper.
Why does pitch matter?
A steeper roof has more surface than its footprint. The calculator multiplies the footprint by √(1 + (pitch/12)²), so a 6/12 roof has about 12% more area than its footprint.
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