How Many Shingles Do I Need? Bundles and Squares

This calculator turns a roof area into shingle bundles. Enter the roof surface area in square feet (the sloped area, not the footprint), a waste allowance and the bundles per square printed on the shingle wrapper; you get the bundles to buy and the roofing squares.

Formula

Squares = roof area × (1 + waste ÷ 100) ÷ 100, because one roofing square covers 100 ft². Bundles = squares × bundles per square, rounded up.

• a: sloped roof area; add every roof plane
• bps: from the wrapper; many three-tab and laminated shingles are 3 bundles per square, some heavier ones 4 or more

Worked Example

A 1,800 ft² roof, 10% waste, 3 bundles per square.

1. Area with waste = 1,800 × 1.10 = 1,980 ft²
2. Squares = 1,980 ÷ 100 = 19.80
3. Bundles = 19.8 × 3 = 59.4, rounded up to 60 bundles

How to read the result

Starter strips and ridge caps are often sold separately; count them from the eaves, rakes and ridge length. Simple gable roofs need about 10% waste; hips, valleys and dormers need more.

Limits and common mistakes

• Use the sloped area. A roof’s footprint is smaller than its surface; multiply by the pitch factor if you only know the footprint.
• Coverage per bundle differs by product; always use the wrapper figure.
• Roof work at height is dangerous; follow safety guidance or hire a roofer.

Frequently Asked Questions

How many bundles are in a square?

Often 3, but check the wrapper; heavy shingles can be 4 or 5.

How many square feet does a bundle cover?

About 33.3 ft² at 3 bundles per square.

How much waste should I add?

About 10% for a simple roof, 15% or more for a complex one.

What is a roofing square?

100 ft² of roof surface.

in a | Roof surface area | ft² | 1800 | 0 | 1000000
in waste | Waste allowance | % | 10 | 0 | 50
in bps | Bundles per square (label) | bundles | 3 | 1 | 10
out bundles | Bundles to buy | bundles | ceil(round(a * (1 + waste / 100) / 100 * bps, 6)) | 0
out sq | Roofing squares (with waste) | squares | a * (1 + waste / 100) / 100 | 2