Roofing calculator
Measure the footprint including the overhangs, then enter the pitch as inches of rise per 12 inches of run.
Your estimateEstimate
- Pitch factor
- 1.118
- Roof area
- 1,342 ft²
- With extra
- 1,476 ft²
- Squares (100 ft² each)
- 14.8
Shingle bundles (3 per square)45
How it is calculated
Pitch factor = √(1 + (rise ÷ 12)²). Roof area = footprint × pitch factor, plus the extra percentage.
A roofing square is 100 ft². Most asphalt shingles come in 3 bundles per square; some heavier styles need more, so check the wrapper.
Worked example
With the starting values shown in the form, the result is 45 (shingle bundles (3 per square)). Change any number and the estimate updates as you type.
Tips
- Hips, valleys and dormers add cutting waste; use 12 to 15% extra on complex roofs.
- Order ridge cap and starter strip separately; they are not included in the bundle count.
Questions
- What is a roofing square?
- 100 square feet of roof surface.
- How many bundles for a 40 × 30 roof at 6/12?
- 1,200 ft² × 1.118 = 1,342 ft² of roof. With 10% extra that is 14.8 squares, or 45 bundles at 3 per square.
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