Roofing Shingle Calculator
Plan a re-roof by the square and the bundle. Enter footprint and pitch for asphalt shingle squares and bundles (3 bundles per square). For individual shingle counts by type, use the Shingle Calculator; for a price-first estimate use Roofing Cost.
Enter your measurements to see what to buy.
How to calculate it
Plan a re-roof by the square and the bundle. Enter footprint and pitch for asphalt shingle squares and bundles (3 bundles per square). For individual shingle counts by type, use the Shingle Calculator; for a price-first estimate use Roofing Cost.
Source: Roofing is measured in “squares” (100 ft²). 3 bundles per square for standard 3-tab and architectural shingles. Pitch factors convert footprint to true surface area.
A 30×40 ft roof footprint (1,200 ft²) at 6/12 pitch (×1.118) with 10% waste: 1,200 × 1.118 × 1.1 = 1,476 ft² = 14.8 squares × 3 = 45 bundles.
Want the full step-by-step walkthrough? Read our How to Calculate Shingles for a Roof.
Roof pitch factors
A sloped roof has more surface area than the flat footprint below it. The pitch factor converts your footprint to true surface area. Use this table to find your factor by roof pitch.
| Roof pitch | Pitch factor | Surface area for 1,000 ft² footprint |
|---|---|---|
| 4/12 | ×1.054 | 1,054 ft² |
| 6/12 | ×1.118 | 1,118 ft² |
| 8/12 | ×1.202 | 1,202 ft² |
| 10/12 | ×1.302 | 1,302 ft² |
| 12/12 | ×1.414 | 1,414 ft² |
One roofing square = 100 ft²; 3 bundles per square for standard 3-tab and architectural shingles. Steeper roofs also need a higher waste allowance.
How to use this calculator
- Enter your roof footprint — the building length × width per roof plane, including overhangs.
- Pick your roof pitch (rise over run, in inches per foot). The calculator applies the pitch factor to convert footprint to true surface area.
- Set your waste allowance — 10% for a simple gable, 15% for hips, valleys and dormers.
- Enter your price per bundle for an optional material cost estimate.
Purchasing & waste guidance
- Measure the footprint (house length × width per roof plane), not the slope surface.
- Use 10% waste for simple gable roofs, 15% for hips, valleys and dormers.
- Steeper roofs need more material and more waste — 12/12 adds 41% over flat.
- Don’t forget underlayment, drip edge, ridge caps and starter strips.
Waste factor guidance
- 10% waste covers cuts and starter/ridge on a simple gable roof.
- Use 15% for hip roofs, valleys and dormers where cuts multiply.
- Steep roofs (12/12 and above) need 15–18% — more cuts and harder handling waste more material.
Common mistakes to avoid
- Measuring the sloped surface instead of the footprint — always use length × width per plane from the ground or attic.
- Forgetting to add waste for hips, valleys and dormers, which create far more cuts than a plain gable.
- Ordering only shingles — underlayment, drip edge, ridge caps and starter strips are separate and easy to miss.
Assumptions & what’s included
- Footprint is the building length × width per roof plane (including overhangs).
- Pitch factor converts footprint to true surface area; 3 bundles per square.
- Waste allowance covers cuts, valleys and starter/ridge. Price is per bundle and optional.
Sources & references
- Roofing squares (100 ft²) and 3 bundles per square follow Asphalt Roofing Manufacturers Association (ARMA) convention for standard 3-tab and architectural shingles.
- Pitch factors converting footprint to true surface area follow standard roof-pitch geometry.
- Waste guidance (10% gable, 15% hips/valleys) follows common roofing trade practice; confirm bundle count on the shingle label.
Learn more about how every calculator works on our methodology page.
Frequently asked questions
How many bundles of shingles do I need for 1,000 sq ft?
1,000 ft² of roof surface is 10 squares, which equals 30 bundles (3 bundles per square). Add 10% waste for a simple gable roof.
How many squares is my roof?
Divide your roof’s true surface area by 100. The calculator applies the pitch factor to your footprint automatically — e.g. a 1,200 ft² footprint at 6/12 is about 13.4 squares.
How does roof pitch affect shingle quantity?
Steeper pitches have more surface area than the footprint below. A 6/12 pitch adds about 12%, an 8/12 adds 20%, and a 12/12 adds 41% — the calculator applies the factor for you.
How many bundles of shingles do I need for a 1,200 sq ft house?
A 1,200 ft² footprint at 6/12 pitch (×1.118) with 10% waste is about 14.8 squares, or 45 bundles of standard shingles. Measure the footprint per roof plane and let the calculator apply your pitch.
How do I measure my roof footprint?
Measure the building length × width for each roof plane, including overhangs — not the sloped surface. For a simple gable that is length × width. For a hip roof, measure each plane and add them. You can do this from the ground or attic.
What is a roofing square?
A roofing square is 100 square feet of roof surface. Standard 3-tab and architectural shingles come 3 bundles per square, so 10 squares equals 30 bundles. The calculator converts your surface area to squares and bundles automatically.
Related guides
Step-by-step project guides that use this calculator.