Calculators
Roofing Calculator
Estimate roofing shingles and bundles to buy from roof size, shingle coverage, and waste allowance locally in your browser.
Enter the roof size and a single shingle's exposed coverage in feet to estimate how many shingles to buy, including a waste allowance for cuts, ridges, valleys, and breakage. The calculation runs locally in your browser; your values are not uploaded or stored.
Enter shingle dimensions in the same unit as the roof; for example, a 36 inch shingle with 5 inch exposure is about 3 by 0.42 ft. This estimate covers one rectangular roof face and ignores pitch, hips, ridges, valleys, flashing, vents, and starter strips, so measure each face separately and add extra waste for complex roofs. Check your supplier because shingle sizes and bundle counts vary by product. This roofing estimate is a planning guide, not a purchase guarantee.
Find how many roofing shingles to buy without uploading anything.
Enter the roof length and width plus a single shingle length and exposed width, an optional shingles-per-bundle count, and a waste allowance to see the roof area, shingle count, and rounded-up bundle count. Everything runs locally in your browser, so your values are not uploaded or stored.
Frequently Asked Questions
Everything you need to know about this tool, how it works, and privacy.
What does the roofing calculator show?
Enter the roof length and width, a single shingle length and exposed width in the same unit, an optional shingles-per-bundle count, and a waste allowance. The calculator returns the roof area, the shingle coverage, and the shingle count with waste rounded up, plus the bundle count when shingles per bundle is given, with the calculation shown. For example, a 30 by 20 ft roof with 3 by 0.42 ft shingles and 10% waste needs about 524 shingles, so buy 18 bundles at 30 shingles per bundle.
Which formula does the roofing calculator use?
It uses roof area = roof length x roof width, shingle coverage = shingle length x shingle exposed width, then shingles = roof area / shingle coverage x (1 + waste percent / 100) rounded up, and bundles = shingles / shingles per bundle rounded up. Use the same length unit for the roof and the shingle; for example, a 36 inch shingle with 5 inch exposure is about 3 by 0.42 ft. The estimate covers one rectangular roof face and ignores pitch, hips, ridges, valleys, flashing, vents, and starter strips, so measure each face separately.
Which inputs are accepted?
Enter a roof length, roof width, shingle length, and shingle exposed width greater than zero through 1000000000, an optional shingles-per-bundle whole number from 1 to 1000000000, and a waste allowance from 0 to 100 percent (blank means 10). Decimal sizes are accepted. Zero sizes, negative numbers, non-numeric text, and values outside these limits show a clear error instead of a result.
Do my numbers stay private?
Yes. The calculation and copy action run locally in your browser. CodeASystem does not upload or store the values you enter.