Build calculator
How many bundles of shingles a roof needs
From the size of the house to roof squares and bundles, plus the underlayment, ice and water shield, ridge cap, starter and drip edge that go with them.
Data last checked . Every source is listed below.
Shingle bundles for the roof
18.5 roofing squares of surface, 1,855 sq ft, plus 10% extra for cuts and leftovers.
- Roof surface
- 1,855 sq ftflat plan 1,659 sq ft x 1.118 for the slope
- Roofing squares (100 sq ft)
- 18.5
- Underlayment rolls (1,000 sq ft)
- 3with 10% for laps
- Ice and water shield rolls (200 sq ft)
- 2a 3 ft strip along the eaves
- Ridge cap bundles
- 225 linear ft each
- Starter strip bundles
- 1105 linear ft each
- Drip edge pieces (10 ft)
- 17round the whole edge
For information only: not advice, a design or a code ruling. We take care, but our sources can lag and so can we, so a figure may be out of date. Package sizes and prices come from the maker and the store, and codes from the local building authority.
What moves the number
The few things that change the answer the most, in plain terms.
- Slope
- A steeper roof has more surface than the floor under it. A 6 in 12 slope adds about 12% to the flat area and a 12 in 12 slope adds about 41%.
- Roof shape and waste
- Valleys, hips and dormers mean more cut shingles. Trade guidance runs from about 10% extra for a plain gable to 15% or more for a complex roof.
- Eaves
- Eaves that stick out past the walls add surface all the way round, about 9% for a one-foot overhang on a typical house.
- Shingle type
- Bundles are counted at three to the square for common architectural shingles. Some lines come in different coverage per bundle; the label governs.
The working
Step by step, with the numbers from the starting example, so you can check it on paper.
- Treat the house as a square of 1,500 sq ft and add 1 ft of eaves on each side: 1,659 sq ft of flat roof.
- Multiply by the slope factor for 6 in 12, sqrt(1 + (6/12)^2) = 1.118: 1,855 sq ft of roof surface, 18.5 squares.
- Add 10% for cuts and leftovers: 2,040 sq ft.
- One bundle covers 33.33 sq ft (three to the square), so 2,040 / 33.33 rounds up to 62 bundles.
- Underlayment: 1,855 sq ft plus 10% for laps over 1,000 sq ft rolls is 3 rolls.
- Ice and water shield: a 3 ft strip along 100 ft of eaves is 299 sq ft, 2 rolls of 200 sq ft.
Try a different case
Each opens the calculator with the numbers filled in.
What we assumed
Where a number is an example, we say so.
- Checked sourceThree bundles to a roofing square: Lowe's lists architectural shingle bundles at 33.33 sq ft each.
- Our estimateThe house is treated as a rectangle 1.5 times as long as it is wide with a gable roof. Extra roof sections, porches, dormers and attached garages with their own roofs add to the area.
- Our estimateWaste of 10%, 15% or 20% follows common trade guidance and varies by installer and roof; it is our rounded range, not a measured figure.
- Published, secondhandRoll and bundle sizes are the common retail sizes (underlayment 1,000 sq ft, ice and water shield about 200 sq ft, ridge cap 25 linear ft, starter strip 105 linear ft, drip edge 10 ft). Check the label of the product you buy.
Sources
- Checked sourceLowe's product pages read on lowes.com, Central Columbus OH store, 5 Nov 2026: architectural shingle bundles of 33.33 sq ft, three to the square; synthetic underlayment 1,000 sq ft rolls; ridge cap 25 linear ft; starter strip 105 linear ft; drip edge 10 ft. Data year 2026, checked 2026-11-05.
- Checked sourceSlope factor: geometry (Pythagoras). The roof surface for a rise per 12 inches of run is the flat plan area times sqrt(1 + (rise/12)^2). Data year 2026, checked 2026-11-05.