Roofing Calculator: Squares & Shingle Bundles
Enter your house size and roof pitch to see roof area, roofing squares, how many bundles of shingles to buy, underlayment rolls and cost.
Tool inputs stay in your browser · optional AI search sends your query
Good to know: Scope: a material estimate for an asphalt shingle roof where every roof plane has the same pitch (simple gable or hip roofs). It works out the sloped roof area, the number of roofing squares (1 square = 100 square feet), the shingle bundles to buy, optional underlayment rolls and the bundle cost. Roof area = flat footprint area (including overhangs) × the pitch multiplier √(1 + (rise ÷ 12)²); these multipliers agree within about 0.01 with the roof slope multiplier table in the State of Michigan Assessor’s Manual (for example 1.12 for 6 in 12 and 1.20 for 8 in 12). Bundles per square: GAF says most standard 3-tab and architectural shingles come 3 bundles to a square and some specialty shingles up to 5; GAF suggests 10 to 15% extra for trim and waste and gives 2:12 as the absolute minimum slope for shingles, with a double layer of underlayment from 2:12 up to 4:12. Felt roll coverage (No. 15: 4 squares, No. 30: 2 squares) is from the ERIC Roofing Workbook. Not included: roofs with planes at different pitches (measure each plane and use “I already know the roof area”), ridge cap, hip and starter shingles, drip edge, flashing, nails, ventilation, tear-off, labor, local prices and building permits. Everything stays in this browser tab; nothing is sent or saved. Independent ToolsKo estimate, not a roofing contractor’s quote. Sources reviewed November 11, 2026.
How to use it (step by step)
- 1Pick how you will measure: the house length and width (easiest, measured on the ground), the flat footprint area in square feet, or the roof surface area if you already measured each roof plane.
- 2Enter the roof pitch as the rise in inches for every 12 inches across, for example 6 for a 6/12 roof, and the overhang of the eaves in inches.
- 3Keep 10% extra (GAF suggests 10 to 15%), choose bundles per square from the shingle wrapper (3 for most shingles) and read the squares and bundles to buy.
Words to know
- Square
- The roofing unit for 100 square feet of roof, a 10 ft × 10 ft patch. Shingles are priced and sold by the square.
- Bundle
- One wrapped pack of shingles, sized so one person can lift it. Most standard shingles take 3 bundles to cover one square.
- Pitch (rise in 12)
- How steep the roof is: how many inches it rises for every 12 inches across. A 6/12 roof rises 6 inches per foot.
- Pitch multiplier
- The number you multiply the flat footprint by to get the real sloped roof area. Steeper roofs have a bigger multiplier, for example 1.12 for 6/12 and 1.41 for 12/12.
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Sources & methods
- GAF: How Many Bundles of Shingles Are in a Square? (1 square = 100 sq ft, 3 bundles per square, up to 5 for specialty shingles, 10 to 15% waste) ↗
- GAF: Minimum Slope for Shingles (2:12 minimum, double underlayment from 2:12 to under 4:12) ↗
- State of Michigan Assessor’s Manual, Roofs (UIP 4): roof slope multipliers to convert horizontal area to roof area ↗
- ERIC (U.S. Department of Education) Roofing Workbook ED219595: square = 100 sq ft, No. 15 felt 4-square rolls, No. 30 felt 2-square rolls ↗
References checked November 11, 2026. Read each tool’s scope and assumptions before relying on its result.