The roof surface is 1,503 ft² (139.6 m²), which with 10% waste is 16.53 squares: 50 bundles of shingles, 4 rolls of #15 felt and 2 bundles of ridge cap for 42 ft of ridge.
Roof cross-section
Nasıl hesaplanır S
Footprint with overhangs
(40+2×1)(30+2×1)=1,344ft2
Slope factor
1+0.52=1.11803
Pitch 6 in 12 = 26.57°. A hip roof with the same pitch on all four sides has the same area factor.
Roof area
1,344×1.11803=1,502.638ft2
Squares and bundles
1001,502.638×1.1=16.529squares×3⇒50bundles
Rounded up to whole bundles.
Underlayment
⌈415.026⌉=4rolls
Roll coverage already allows for laps; rounded up to whole rolls.
Ridge
ridge=42ft
Ridge cap: 42 ft ÷ 25 ft per bundle, rounded up to 2.
Roofing and shingle calculator hakkında
Roof area is the footprint including overhangs multiplied by the slope factor √(1 + (rise ÷ 12)²), which turns plan area into sloped surface. A hip roof with the same pitch on all four sides has the same factor as a gable. Area plus waste is divided into squares of 100 ft² and multiplied by bundles per square; the ridge and hip length divided by the coverage of one ridge-cap bundle gives the ridge bundles.
The default 40 × 30 ft gable with 1 ft overhangs at a 6/12 pitch has a slope factor of 1.118 and 1,502.64 ft² of roof. With 10% waste that is 16.53 squares, or 50 bundles at three per square, plus 4 rolls of #15 felt and 2 bundles of ridge cap.
The pitch is checked against the asphalt-shingle slope rules in 2021 IRC R905.2.2. Valleys, dormers, starter strip and drip edge are not counted.
Doğrulama kaynağı: Python math: 11 × 9 m ÷ cos 30° = 114.3154 m² = 1230.48 ft² × 1.1 ÷ 100 × 3 = 40.6 → 41
Sorular
How many bundles of shingles do I need?
Divide the roof area by 100 to get squares, add waste, and multiply by the bundles per square printed on the wrapper (three is the default here). A 40 × 30 ft gable with 1 ft overhangs at 6/12 has 1,502.64 ft² of roof, or 16.53 squares with 10% waste: 49.6 bundles, bought as 50. The waste presets are 10% for gables and 15% for hips, where every course is cut along the hips.
How do you convert roof pitch to degrees and a slope factor?
Pitch is the rise in inches per 12 in of run. A 6/12 roof rises at arctan(6 ÷ 12) = 26.57°, and its slope factor √(1 + 0.5²) = 1.118 means each square foot of plan carries 1.118 ft² of roof. A 4/12 roof is 18.43° with a factor of 1.054; a 12/12 roof is 45° with a factor of 1.414.
What is the minimum roof pitch for asphalt shingles?
2:12, about 9.5°. Under 2021 IRC R905.2.2, asphalt shingles may be used only on slopes of 2 in 12 or steeper, and slopes from 2:12 up to 4:12 need double underlayment. Flatter roofs need a low-slope covering such as a membrane. In the 2:12 to 4:12 range this calculator doubles the underlayment rolls.
What is a roofing square?
100 ft² of roof surface, about 9.29 m². Shingles and underlayment are ordered by the square, so a roof of 1,502.64 ft² is 15.03 squares before waste and 16.53 after 10% waste. With the #15 felt option at 4 squares per roll, that roof takes 4 rolls of underlayment.
How do you calculate the area of a hip roof?
Use the same slope factor as a gable: when all four sides share one pitch, sloped area = plan area × √(1 + (rise ÷ 12)²). A 40 × 30 ft hip roof at 6/12 with no overhang is 1,200 × 1.118 = 1,341.64 ft². Its ridge is 40 − 30 = 10 ft and each of the four hips is 22.5 ft, so ridge cap covers 100 ft.
“Roofing and shingle calculator” ne kadar doğru sonuç verir?
Doğruluk, girdilerinize ve yöntemin varsayımlarına bağlıdır. Ondalık aritmetik 50 anlamlı basamak kullanır; ancak tahminler, sayısal yöntemler ve kaynak veriler daha az hassas olabilir. Gösterilen değerin yuvarlanması bu sınırları ortadan kaldırmaz. Bağımsız kaynaklarla doğrulanan çözümlü örnek sayısı: 4. Örneğin “40 × 30 ft gable, 1 ft overhang, 6/12, 10% waste”, Python decimal: 42 × 32 × √1.25 = 1502.64 ft²; × 1.1 ÷ 100 × 3 = 49.59 → 50 bundles; 15.03 squares ÷ 4 → 4 rolls ile karşılaştırılarak doğrulanır.
Yöntemin kaynağı nedir?
International Code Council — 2021 IRC R905.2.2: asphalt shingles on slopes of 2:12 or steeper, double underlayment from 2:12 up to 4:12; GAF Seal-A-Ridge — 25 linear ft per bundle; Owens Corning ProEdge — 33 linear ft per bundle.