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Roofing and shingle calculator

Roof area, squares and shingle bundles from building size and pitch, with underlayment rolls, ridge cap and the IRC minimum slope check.

Обновлено Проверенные примеры: 4

in 12
%
Другие параметры
Three bundles cover one square (100 ft²) for most 3-tab and architectural shingles.
Read it on the wrapper: GAF Seal-A-Ridge covers about 25 ft, Owens Corning ProEdge about 33 ft.
Попробовать
Shingle bundles to buy
bundles
Shingle bundles to buy: 50 bundles
Целое число; В сторону плюс бесконечности
Roof area
1,502.6ft² / 139.6m²
Squares with waste
16.53squares
Underlayment rolls
4rolls
Ridge and hip length
42.0ft / 12.8m
Ridge cap bundles
2bundles
Pitch angle
26.6°
Slope factor
1.1180

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

32 ft (9.75 m) with overhangsrise 8 ft (2.44 m)rafter 17.89 ft (5.45 m)26.6°
Как выполняется расчёт S

  1. Footprint with overhangs

    (40+2×1)(30+2×1)=1,344 ft2(40 + 2 \times 1)(30 + 2 \times 1) = 1{,}344\ \text{ft}^2

  2. Slope factor

    1+0.52=1.11803\sqrt{1 + 0.5^2} = 1.11803

    Pitch 6 in 12 = 26.57°. A hip roof with the same pitch on all four sides has the same area factor.

  3. Roof area

    1,344×1.11803=1,502.638 ft21{,}344 \times 1.11803 = 1{,}502.638\ \text{ft}^2

  4. Squares and bundles

    1,502.638×1.1100=16.529 squares×3⇒50 bundles\frac{1{,}502.638 \times 1.1}{100} = 16.529\ \text{squares} \times 3 \Rightarrow 50\ \text{bundles}

    Rounded up to whole bundles.

  5. Underlayment

    ⌈15.0264⌉=4 rolls\left\lceil \frac{15.026}{4} \right\rceil = 4\ \text{rolls}

    Roll coverage already allows for laps; rounded up to whole rolls.

  6. Ridge

    ridge=42 ft\text{ridge} = 42\ \text{ft}

    Ridge cap: 42 ft ÷ 25 ft per bundle, rounded up to 2.

О калькуляторе: Roofing and shingle calculator

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.

Примеры с решением

40 × 30 ft gable, 1 ft overhang, 6/12, 10% waste

Roof type
Gable
Building length
40 ft
Building width
30 ft
Overhang on each side
1 ft
Pitch given as
Rise per 12
Pitch
6 in 12
Waste allowance
10%
Underlayment
#15 felt (4 squares per roll)
Roof area
1,502.6 ft²
Squares with waste
16.53 squares
Shingle bundles to buy
50 bundles
Underlayment rolls
4 rolls
Ridge and hip length
42.0 ft
Ridge cap bundles
2 bundles
Pitch angle
26.6 °

Источник проверки: Python decimal: 42 × 32 × √1.25 = 1502.64 ft²; × 1.1 ÷ 100 × 3 = 49.59 → 50 bundles; 15.03 squares ÷ 4 → 4 rolls

Hip roof 40 × 30 ft, 6/12, no overhang or waste

Roof type
Hip
Building length
40 ft
Building width
30 ft
Overhang on each side
0 ft
Pitch given as
Rise per 12
Pitch
6 in 12
Waste allowance
0%
Underlayment
#15 felt (4 squares per roll)
Roof area
1,341.6 ft²
Ridge and hip length
100.0 ft
Shingle bundles to buy
41 bundles

Источник проверки: Hand calculation: ridge 40 − 30 = 10 ft; each hip √(2 × 15² + 7.5²) = 22.5 ft, × 4 = 90 ft; 1200 × 1.118034 = 1341.64 ft²

Edge: 12/12 pitch is 45°

Roof type
Gable
Building length
30 ft
Building width
20 ft
Overhang on each side
0 ft
Pitch given as
Rise per 12
Pitch
12 in 12
Waste allowance
0%
Underlayment
#15 felt (4 squares per roll)
Roof area
848.5 ft²
Pitch angle
45.0 °
Slope factor
1.4142
Shingle bundles to buy
26 bundles

Источник проверки: Hand calculation: slope factor √2 = 1.41421; 600 × √2 = 848.53 ft² → 25.46 → 26 bundles

30° roof on a 10 × 8 m house, 0.5 m overhang

Roof type
Gable
Building length
10 m
Building width
8 m
Overhang on each side
0.5 m
Pitch given as
Градусы
Pitch angle
30 °
Waste allowance
10%
Underlayment
#15 felt (4 squares per roll)
Roof area
114.32 m²
Shingle bundles to buy
41 bundles

Источник проверки: Python math: 11 × 9 m ÷ cos 30° = 114.3154 m² = 1230.48 ft² × 1.1 ÷ 100 × 3 = 40.6 → 41

Вопросы

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.

Насколько точен «Roofing and shingle calculator»?

Точность зависит от введённых данных и допущений метода. Десятичная арифметика использует 50 значащих цифр, но оценки, численные методы и исходные данные могут быть менее точными; округление на экране не устраняет эти ограничения. Решённые примеры, проверенные по независимым источникам: 4. Например, «40 × 30 ft gable, 1 ft overhang, 6/12, 10% waste» проверяется по источнику Python decimal: 42 × 32 × √1.25 = 1502.64 ft²; × 1.1 ÷ 100 × 3 = 49.59 → 50 bundles; 15.03 squares ÷ 4 → 4 rolls.

Откуда взята методика?

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.

Об этом калькуляторе

A=(L+2o)(W+2o)1+(p/12)2,bundles=⌈3⋅A(1+waste)100⌉A = (L + 2o)(W + 2o)\sqrt{1 + (p/12)^2},\qquad \text{bundles} = \left\lceil 3 \cdot \frac{A (1 + \text{waste})}{100} \right\rceil

Источники

  1. 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
  2. GAF Seal-A-Ridge — 25 linear ft per bundle; Owens Corning ProEdge — 33 linear ft per bundle

Проверено по источникам

В калькулятор включены решённые примеры с ответами из независимых источников. Их количество: 4. Они входят в набор тестов, и вы также можете запустить их здесь.

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