Roofing Calculator
Enter your roof footprint and pitch to estimate the roof area, number of roofing squares, and shingle bundles needed.
Results
- Roof area
- 1,475.8 sq ft
- Roofing squares
- 14.76 squares
- Shingle bundles
- 45 bundles
Estimates only. Round up and buy a little extra to account for waste, spills, and breakage.
Enter your roof footprint and pitch to estimate the roof area, number of roofing squares, and shingle bundles needed.
Also used as a shingle calculator and roofing squares estimator.
How to use the roofing calculator
- Enter the footprint length in ft.
- Enter the footprint width in ft.
- Enter the pitch (rise per 12) in /12.
- Enter the waste factor in %.
- Optionally add a price to estimate the total project cost.
- Read your quantities instantly — no sign-up, and you can print the estimate to take to the supplier.
Worked example
Inputs
- Footprint length
- 40 ft
- Footprint width
- 30 ft
- Pitch (rise per 12)
- 6 /12
- Waste factor
- 10 %
Results
- Roof area
- 1,475.8 sq ft
- Roofing squares
- 14.76 squares
- Shingle bundles
- 45 bundles
Using the example values above, the roofing calculator returns 1,475.8 sq ft (roof area). Change any field to match your own project and the numbers update instantly.
How much extra should I order?
Always order a little extra. A 5% waste factor suits simple, square projects; 10% is right for most jobs; bump it to 15–20% for irregular shapes, diagonal patterns, or uneven ground. Running short almost always costs more than the leftover material.
Pitch multipliers
| Pitch | Multiplier | Angle |
|---|---|---|
| 3/12 | 1.031 | 14.0° |
| 4/12 | 1.054 | 18.4° |
| 6/12 | 1.118 | 26.6° |
| 8/12 | 1.202 | 33.7° |
| 12/12 | 1.414 | 45.0° |
Formula
Roof area = footprint × pitch multiplier. Squares = area ÷ 100. Bundles = squares × 3, plus waste.
Frequently asked questions
- What is a roofing square?
- A square equals 100 square feet of roof area; shingles are sold three bundles per square.
- How does pitch change the amount?
- Steeper roofs have more surface area than their footprint, so the pitch multiplier increases the material needed.
- How many bundles of shingles do I need?
- Most architectural shingles come three bundles per square (100 sq ft). Divide your roof area by 100 and multiply by three.
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Roof Pitch Chart
Roof pitch multipliers used to convert footprint to roof area.