Start with surface area, then read the packaging
Shingles cover the sloping roof surface rather than the horizontal building footprint. Enter a measured surface area or obtain it from a separate pitch-and-footprint calculation. This form does not apply another pitch factor. Each field bundle has a stated installed coverage that accounts for the intended exposure. Use that coverage rather than the sum of the individual shingle dimensions, which includes overlapping material.
Keep field, cap and starter products distinct
Field bundles = ceiling(area × (1 + allowance ÷ 100) ÷ coverage per bundle)The field allowance applies only to the main roof area. Ridge and hip caps are counted from linear length and their own package coverage. Starter strips use another linear coverage figure. These three package counts are rounded independently, because unused field bundles cannot automatically replace specialty components. The cap and starter lengths should already reflect any extra quantity required by their actual layout.
A one hundred square metre takeoff
For 100 square metres of sloping surface, a ten percent cutting allowance gives 110 square metres. If the field product covers 3 square metres per bundle, 36.667 bundles are needed mathematically, so buy 37. A 10 metre cap run with 8 metres per package needs two cap packages. Thirty metres of starter edges with 20 metres per package needs two starter packages. These are separate purchasing lines rather than one total.
Match the system and installation details
Do not assume all shingles come in three bundles per square: heavier or specialty products may have different coverage. Follow the selected manufacturer's compatible cap and starter system. Complex valleys, dormers and diagonal cuts can change field waste substantially. Count all edges that require starter under the product's instructions, and measure hips as well as ridges where they need caps. The calculator does not specify flashing, nails, underlayment, ventilation or substrate repairs. If an accessory is not used, set its required length to zero while leaving its package coverage positive. Keep the original takeoff and labels so an installer can check assumptions and distinguish extra field material from missing accessory items.
Frequently asked questions
Do I enter footprint or sloping area?
Enter actual sloping roof area. Use the roof-square calculator first if you only know a projected footprint and pitch.
How many bundles cover a roofing square?
It depends on the product's stated bundle coverage. A roofing square is 100 square feet; divide that area by the coverage on the label.
Can ridge length be zero?
Yes. A zero cap length produces zero cap packages. The package-coverage field must remain positive to define the conversion.
Does waste apply to starter strips?
No. The editable percentage increases field area only. Include any required extra length in the starter and cap takeoff.
Are nails included?
No. Fastener counts depend on the product and fastening pattern. Check the installation instructions separately for nails and accessories.
Last reviewed: 2026-10-05 · How we calculate