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Roofing calculator for contractors: squares, pitch and bundles
The short answer
To work out roofing squares, multiply the building’s length by its width, including overhangs, multiply by the pitch factor, then divide by 100. One square covers 100 square feet. A 40 by 30 foot house at a 6/12 pitch (factor 1.118) is about 13.4 squares. Add 10 to 15% for waste. Most shingles come in three bundles a square.
Enter the building’s size and the roof’s pitch to get the squares and what to order: shingle bundles, underlayment, ridge cap, starter and drip edge. Use it for a quick number before you quote, then measure on site.
What to order
13.4 squares
1,342 square feet of roof, from a 1,200 square foot footprint × 1.118.
- Squares with waste
- 14.8
- Bundles of shingles
- 45
- Rolls of underlayment
- 4
An estimate for one pitch across the whole roof. Measure on site before you order: dormers, valleys and a second pitch change the numbers. Whole bundles and rolls are rounded up.
Roof pitch
6/12
- Angle
- 26.6°
- Pitch factor
- 1.118
How it works
- Measure the building’s length and width, including the overhangs.
- Enter the pitch. Don’t know it? Measure it with a level and use “Find the pitch”.
- Set the waste: often about 10% on a simple gable, 15% or more on a hip or a cut-up roof.
- Add the ridge, hip, eave and rake lengths to get cap, starter and drip edge.
- Check the coverage on the product’s label and change it if it’s different.
The math: footprint × pitch factor = roof area, and roof area ÷ 100 = squares. It assumes one pitch across the whole roof, so measure each section on its own if the pitch changes. Ready to price it? Put it on the estimate template, and use the markup calculator for your materials.
Roof pitch factors
| Pitch | Factor | Angle |
|---|---|---|
| 3/12 | 1.031 | 14° |
| 4/12 | 1.054 | 18.4° |
| 5/12 | 1.083 | 22.6° |
| 6/12 | 1.118 | 26.6° |
| 7/12 | 1.158 | 30.3° |
| 8/12 | 1.202 | 33.7° |
| 9/12 | 1.250 | 36.9° |
| 10/12 | 1.302 | 39.8° |
| 12/12 | 1.414 | 45° |
Storm work means calls come in while you’re up on a roof. See how an answering service for roofers works.
Common questions
How do you calculate roofing squares?
What is a square in roofing?
How many bundles of shingles are in a square?
How much waste should I add for shingles?
How do I find a roof’s pitch?
Is this calculator accurate enough to order from?
Does it work on a phone?
More free tools
Estimate template
Fill in an estimate or quote, then print it or save it as a PDF.
Markup and margin calculator
Price products and jobs at the margin or markup you want, and see the difference.
Change order template
Put added work and its cost in writing, with the new total and both signatures.
Can’t answer from the roof?
CoveDesk answers your calls when you can’t and texts you who called and what they need, so you can call back when you’re down.