# Roofing Calculator > Free roofing calculator: turn the house footprint and roof pitch into roof area, squares and shingle bundles with waste. Formula and pitch table shown. Canonical: https://brickbyclick.ai/roofing-calculator Last updated: 2026-10-28 ## Roof square footage calculator Measure the outside of the house at the eaves, or the footprint plus the overhang on every side. Choose the pitch and the calculator does the rest. Shingles only. Order starter strip, ridge cap, underlayment, drip edge and nails separately, and check every number against the manufacturer's coverage on the bundle. ## How to calculate roof squares A roof is longer than the floor under it because it slopes. The pitch factor is how much longer. It comes straight from the right triangle that the rise and run make: pitch factor = √(1 + (rise ÷ 12)²) roof area = footprint area × pitch factor squares = roof area ÷ 100 bundles = squares × (1 + waste %) × bundles per square, rounded up ### Worked example A house measures 40 ft by 30 ft at the eaves, with a 6/12 roof and 10% waste. 1. Footprint: 40 × 30 = 1,200 sq ft. 2. Pitch factor for 6/12: √(1 + 0.5²) = √1.25 = 1.1180. 3. Roof area: 1,200 × 1.1180 = 1,341.6 sq ft. 4. Squares: 1,341.6 ÷ 100 = 13.42. 5. With 10% waste: 13.42 × 1.10 = 14.76 squares. 6. Bundles: 14.76 × 3 = 44.3, so order **45 bundles**. Those are the numbers the calculator above opens with, so you can check it. ### Why the footprint method works for hip roofs too If every face of the roof has the same pitch, the sloped area is always the flat footprint times the same pitch factor, whether the roof is a gable, a hip or a mix. That is why you can measure from the ground. If parts of the roof have different pitches, work out each part on its own and add them up. ## Roof pitch multiplier table Multiply the footprint by the factor for your pitch. The last column shows the roof area over a 1,000 sq ft footprint. *Pitch factor = √(1 + (rise ÷ 12)²)* | Pitch | Factor | Angle | On 1,000 sq ft | | --- | --- | --- | --- | | 0/12 | 1.0000 | 0.0° | 1,000 sq ft | | 1/12 | 1.0035 | 4.8° | 1,003 sq ft | | 2/12 | 1.0138 | 9.5° | 1,014 sq ft | | 3/12 | 1.0308 | 14.0° | 1,031 sq ft | | 4/12 | 1.0541 | 18.4° | 1,054 sq ft | | 5/12 | 1.0833 | 22.6° | 1,083 sq ft | | 6/12 | 1.1180 | 26.6° | 1,118 sq ft | | 7/12 | 1.1577 | 30.3° | 1,158 sq ft | | 8/12 | 1.2019 | 33.7° | 1,202 sq ft | | 9/12 | 1.2500 | 36.9° | 1,250 sq ft | | 10/12 | 1.3017 | 39.8° | 1,302 sq ft | | 11/12 | 1.3566 | 42.5° | 1,357 sq ft | | 12/12 | 1.4142 | 45.0° | 1,414 sq ft | | 14/12 | 1.5366 | 49.4° | 1,537 sq ft | | 16/12 | 1.6667 | 53.1° | 1,667 sq ft | | 18/12 | 1.8028 | 56.3° | 1,803 sq ft | | 24/12 | 2.2361 | 63.4° | 2,236 sq ft | ### How to find your roof pitch Hold a level flat against the underside of a rafter or on the roof surface, mark 12 inches along it, and measure straight up (or down) from that mark to the roof. That many inches is the rise, so 6 inches means a 6/12 pitch. A phone angle app works too: 26.6° is 6/12, and the table above lists the rest. ## How many bundles of shingles per square? A roofing square is 100 sq ft of roof. Most asphalt shingles, 3-tab and many architectural lines, come three bundles to the square, about 33.3 sq ft per bundle; Owens Corning lists its Supreme 3-tab at 33.3 sq ft per bundle, for example. Some heavier designer shingles need four or five bundles per square, so read the coverage on the wrapper and set it in the calculator. - **Waste:** you lose shingle at every cut, valley and hip. A plain gable wastes little; a cut-up roof wastes more. Set the percentage to match the roof. - **Starter and ridge:** these are bought by the linear foot of eave, rake, hip and ridge, not by area. - **Tear-off:** if you are removing layers, price the disposal by the square too. ## Turning a roofing estimate into a quote Materials are only part of the price. Add labour, disposal, permits and your margin. The [margin calculator](https://brickbyclick.ai/margin-calculator) turns your cost into a price at the margin you want, and [job costing](https://brickbyclick.ai/job-costing) shows what each roof made after the work is done. When the customer says yes, send the bill with the [free invoice generator](https://brickbyclick.ai/free-invoice-generator), or use [BrickByClick Free](https://brickbyclick.ai/free-invoicing) to email it with a card payment link for $0 a month. [Starter, $99 a month](https://brickbyclick.ai/starter-plan), adds estimates customers accept online, a job tracker and a calendar. ## Sources - Pitch factor: the Pythagorean theorem applied to a 12-inch run, as used by roofing calculators such as [Jobber’s roof shingle calculator](https://www.getjobber.com/free-tools/roof-shingle-calculator/) (√(rise² + run²) ÷ run). - Bundle coverage: [Owens Corning Supreme 3-tab, 33.3 sq ft per bundle](https://www.homedepot.com/p/Owens-Corning-Supreme-Shasta-White-3-Tab-Asphalt-Roofing-Shingles-33-3-sq-ft-per-Bundle-SA12/205655950) (three bundles per 100 sq ft square). Always use the coverage on your product’s wrapper. - Square foot and square metre: 1 m = 3.28084 ft, so 1 m² = 10.7639 sq ft, from [NIST Handbook 44, Appendix C (General Tables of Units of Measurement)](https://www.nist.gov/pml/owm/publications/nist-handbooks/handbook-44). ## Questions people ask ### How do I calculate how many squares my roof is? Multiply the footprint (length times width at the eaves) by the pitch factor for your roof, then divide by 100. A 1,200 sq ft footprint with a 6/12 pitch is 1,200 × 1.118 = 1,341.6 sq ft, or 13.4 squares before waste. ### How many bundles of shingles are in a square? Most asphalt shingles are three bundles per square, so each bundle covers about 33.3 sq ft. Some heavy designer shingles are four or five bundles per square, so check the coverage printed on the wrapper. ### What is a roof pitch factor? It is how much longer the sloped roof is than the flat footprint under it. It equals the square root of 1 plus (rise divided by 12) squared. A 6/12 roof has a factor of 1.118, so it is about 11.8% bigger than its footprint. ### How much waste should I add for shingles? It depends on the roof. A simple gable has few cuts and little waste. Hips, valleys and dormers mean more cutting, so add more. The calculator lets you set the percentage; check with your supplier for the shingle you use. ### How do I measure a roof from the ground? Measure the outside of the house and add the overhang on each side, or measure at the drip edge. Multiply length by width to get the footprint, then use the pitch factor. This works whenever all faces of the roof share one pitch. ### Does the calculator work for a hip roof? Yes, if every face has the same pitch. The sloped area of a hip roof is its footprint times the pitch factor, the same as a gable. If parts of the roof have different pitches, work out each part separately and add them. ### How do I find my roof pitch? Put a level against a rafter or on the roof, mark 12 inches along it, and measure straight up to the roof. That rise in inches over 12 is the pitch. On an angle app, 18.4 degrees is 4/12, 26.6 degrees is 6/12 and 45 degrees is 12/12. ### How many square feet does a bundle of shingles cover? At three bundles per square, one bundle covers about 33.3 sq ft of roof. At four bundles per square it is 25 sq ft. The exact coverage is printed on the bundle. ### Does this include ridge cap, starter strip and underlayment? No. It counts field shingles only. Ridge cap and starter strip are bought by the linear foot of ridge, hip, eave and rake, and underlayment by the roll coverage on its label. ### How do I turn the estimate into a price for the customer? Add labour, disposal, permits and your margin to the material cost. The [margin calculator](https://brickbyclick.ai/margin-calculator) gives a price from cost and target margin, and [BrickByClick Starter](https://brickbyclick.ai/starter-plan) sends estimates customers accept online. ## Related - [Margin calculator](https://brickbyclick.ai/margin-calculator): Margin, markup and price from cost. - [Receipt maker](https://brickbyclick.ai/receipt-maker): Make a payment receipt and save it as a PDF. - [Google Docs invoice template](https://brickbyclick.ai/google-docs-invoice-template): An invoice template that opens in Google Docs. - [Word invoice template](https://brickbyclick.ai/word-invoice-template): A Microsoft Word invoice template to download. - [Proforma invoice template](https://brickbyclick.ai/proforma-invoice-template): What a proforma invoice is, with a template. - [Duct calculator](https://brickbyclick.ai/hvac-duct-calculator): Round and rectangular duct size from CFM and velocity. - [Pipe volume calculator](https://brickbyclick.ai/pipe-volume-calculator): Gallons and litres in a pipe run. - [Square footage calculator](https://brickbyclick.ai/square-footage-calculator): Area of rooms and lots, and square feet to acres. - [How to leave a Google review](https://brickbyclick.ai/how-to-leave-a-google-review): Steps for customers, and a review link builder. - [Google Local Services Ads](https://brickbyclick.ai/google-local-services-ads): How Local Services Ads work for service businesses.