Roofing is measured in squares — 100 sq ft each. Divide the roof area by 100 for squares, add waste, and multiply by bundles-per-square to order shingles.
The example
2,400 ft² roof + 10%.
| A | B | |
|---|---|---|
| 1 | Item | Value |
| 2 | Squares | 24 |
| 3 | +10% → bundles | → 80 bundles |
The formula
The formula:
How it works
How it works:
- A roofing square covers 100 sq ft — divide roof area by 100.
- Use the actual roof surface area (including pitch), not the building footprint.
- Add waste (10–15%) for cuts, ridge, hip, and starter courses.
- Most architectural shingles run 3 bundles per square — multiply to order bundles.
Pitch makes the roof bigger than the footprint. A steeper roof has more surface area than the floor below it. Multiply the footprint by a pitch factor (e.g. ~1.12 for 6/12, ~1.25 for 9/12) before dividing by 100, or measure the actual slope lengths. Estimating from footprint alone undercounts every time.
Try it: interactive demo
Roof area (ft²), waste %, bundles per square.
Variations
Bundles to order
Squares × 3:
Pitch-adjusted area
Footprint × factor:
Material cost
Squares × price:
Pitfalls & errors
Use roof surface. Account for pitch — footprint understates the area.
1 square = 100 ft². Divide by 100, not 10.
Bundles per square vary. 3 is typical; check the product (some need 4).
Practice workbook
Frequently asked questions
How do I calculate roofing squares in Excel?
How many bundles are in a square?
Why use roof area instead of the footprint?
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