Calculators
Roofing Calculator
Calculate roof area from the footprint and pitch, roofing squares, shingle bundles, underlayment and nails.
- Runs in your browser
- Nothing uploaded
The tool
Enter your numbers below. Results update as you type, and nothing leaves your browser.
Everything you enter stays on your own machine. Nothing is sent to us or to anyone else, which you can confirm in your browser network tab.
What people use it for
- Ordering shingles for a re-roof
- Checking a roofing quote
- Estimating materials for a new build
- Comparing roofing products
About this tool
What the Roofing Calculator does
Roof area is the building footprint (including overhangs) multiplied by a pitch factor, because a sloped roof has more surface than the ground it covers. Roofers count in squares of 100 sq ft; most asphalt shingles come three bundles to the square.
It also works as a roofing shingle calculator or a roof square calculator.
Formula
- Pitch factor = √(1 + (rise ÷ 12)²)
- Roof area = footprint × pitch factor
- Squares = area × (1 + waste) ÷ 100; bundles = squares × bundles per square
Worked example
Using the starting values in the calculator above:
| Input | Value |
|---|---|
| Footprint length including overhang | 40 ft |
| Footprint width including overhang | 30 ft |
| Roof pitch | 6/12 |
| Waste allowance | 10% |
| Bundles per square | 3 |
| Underlayment coverage per roll | 1,000 sq ft |
| Result | Value |
|---|---|
| Roofing squares with waste | 14.8 |
| Shingle bundles | 45 |
| Roof surface area | 1,342 |
| Underlayment rolls | 2 |
| Roofing nails | 36.9 |
| Pitch factor | 1.118 |
How to read the result
Complex roofs with hips, valleys and dormers waste more material; 15% or more is common.
Ridge caps and starter strips are usually ordered separately by linear foot.
Quantities are estimates. Check product data sheets and local codes, and confirm with your supplier before ordering.
Related calculators
- Roofing Labour Cost Estimator: Estimate a roof replacement price from squares, labour, tear-off, pitch difficulty, materials, disposal, permits and markup.
- Tile Calculator: Calculate how many tiles and boxes you need for a floor or wall from the area, tile size, grout joint and waste.
- Flooring Installation Cost Calculator: Estimate flooring installation cost from area, material and labour prices per square foot, underlayment, removal, baseboards and transitions.
- Deck Material Calculator: Calculate deck boards, linear feet, joists and screws for a rectangular deck from size, board width, gap and joist spacing.
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Questions
Questions about this tool
The things clients actually want to know — costs, timelines, ownership and what happens after launch.
100 square feet of roof surface.
Most three-tab and architectural shingles come in three bundles per square; check the wrapper.
Measure the vertical rise over a 12-inch horizontal run, for example 6 inches gives a 6/12 pitch.
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- Response time
- Within 1 business hour
- Where we work
- UK, USA & the Gulf
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- Working since
- 2023