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Roofing Calculator
Enter the footprint of the roof and its pitch to estimate the true roof surface, the number of roofing squares and the bundles of shingles to order. A waste allowance covers starter strips, ridge caps and cuts.
One square = 100 sq ft; includes waste.
- Bundles of shingles
- 45
- Roof surface area
- 1,341.64 ft²
- Pitch multiplier
- 1.118
- Shingle cost
- $1,575.00
Saved setups
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Your recent calculations
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Formula
How to use it
- Measure the building footprint including the roof overhangs and enter length and width.
- Enter the roof pitch as inches of rise per 12 inches of run.
- Set waste: 10% for a plain gable, 15% for hips and valleys.
- Read the squares and bundles; add a price per bundle for cost.
Worked examples
A 40 × 30 ft footprint with a 6/12 pitch and 10% waste at $35 a bundle
- Pitch multiplier
- 1.118
- Roof surface area
- 1,341.64 ft²
- Roofing squares to order
- 14.76
- Bundles of shingles
- 45
- Shingle cost
- $1,575.00
A 50 × 24 ft footprint with a 4/12 pitch and 15% waste
- Pitch multiplier
- 1.054
- Roofing squares to order
- 14.55
- Bundles of shingles
- 44
- Shingle cost
- $1,540.00
Pitch multipliers
3/12: 1.031. 4/12: 1.054. 5/12: 1.083. 6/12: 1.118. 8/12: 1.202. 10/12: 1.302. 12/12: 1.414. Multiply the flat footprint by the multiplier to get the sloped surface. The same multiplier works for gable and hip roofs of the same pitch.
Squares and bundles
Roofers measure in squares: one square is 100 sq ft of roof. Standard three-tab and most architectural shingles come three bundles to the square; some heavy premium shingles take four or five, so check the wrapper and change the setting if needed.
This estimate covers field shingles. You will also need underlayment, drip edge, starter strip, ridge caps and nails, and a complex roof is best measured plane by plane.
Questions people ask
How many bundles of shingles do I need for 1,500 square feet?
1,500 sq ft of roof is 15 squares, which is 45 bundles at three per square. With 10% waste, order 50 bundles.
How many square feet does a bundle of shingles cover?
About 33.3 sq ft, since three bundles cover one 100 sq ft square.
How do I work out roof area from the house footprint?
Multiply the footprint, including overhangs, by the pitch multiplier. A 40 × 30 ft footprint with a 6/12 roof is 1,200 × 1.118 = 1,342 sq ft.