Free roofing calculator by address
Find your building or enter its dimensions to estimate roof area, roofing squares and shingle bundles. Free, with no signup.
Roof details
Type your address or .
Calculate pitch from rise / run
Hold a level flat with one end on the roof or a rafter. Mark 12 inches along the level, then measure straight down from that mark to the roof. That number is the rise.
Extra material for cuts and overlaps. Complex roofs may need a higher allowance.
Your estimate
Ready when you areStart with your roof
Find an address to see the estimated roof area and materials you’ll need.
- Roof area
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- Roofing squares
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- Shingle bundles
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Download your estimate as a free PDF.
Need every roof face measured?
Turn drone photos into a measurable 3D scan, with findings and a customer-ready report. Any pilot can upload to your job.
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What the roofing calculator gives you
Most roof calculators ask you to measure first. This one starts from the address, so you have numbers for a quote before anyone drives to the house.
Finds the building for you
Type an address and the building is outlined on a satellite view. There is nothing to draw and no tape measure to pull.
Every side measured
The length of each side of the outline is written on the map, with the footprint and the distance around the building.
Roof area from the pitch
Pick the pitch, or work it out from a level and a ruler, and the footprint is turned into the real sloped area of the roof.
Squares and bundles
Roof area becomes roofing squares, squares with a waste allowance, and the number of shingle bundles to order.
More than one building
Click a detached garage, a shed or the next block to add it. Click again to take it out. The totals follow.
Take it with you
Download the estimate as a PDF with the outline drawing, and the outline itself as a KML file for a map or a flight plan.
How to calculate the area of a roof
The calculator follows four steps that you can also do on paper.
1. Measure the footprint
The footprint is the area the building covers on the ground, out to the edge of the roof. For a simple rectangle it is length times width. A house that is 40 feet by 30 feet has a footprint of 1,200 square feet.
2. Multiply by the pitch factor
A sloped roof is bigger than the ground under it. The pitch factor says how much bigger. A 6/12 roof has a factor of 1.118, so 1,200 square feet of footprint is 1,342 square feet of roof.
3. Divide by 100 to get squares
Roofing is sold by the square, and one square covers 100 square feet. 1,342 square feet is 13.4 squares.
4. Add waste and count bundles
Add an allowance for cuts and mistakes. With 10 percent waste, 13.4 squares becomes 14.8. At three bundles to a square that is 45 bundles of shingles.
Roof pitch factor table
Roof pitch is written as rise over run: a 6/12 roof climbs 6 inches for every 12 inches it runs. Multiply the footprint by the factor to get the roof area. The factor is also called a roof pitch multiplier.
| Pitch | Angle | Pitch factor | Roof over 1,000 sq ft |
|---|---|---|---|
| 1/12 | 4.8° | 1.003 | 1,003 sq ft |
| 2/12 | 9.5° | 1.014 | 1,014 sq ft |
| 3/12 | 14.0° | 1.031 | 1,031 sq ft |
| 4/12 | 18.4° | 1.054 | 1,054 sq ft |
| 5/12 | 22.6° | 1.083 | 1,083 sq ft |
| 6/12 | 26.6° | 1.118 | 1,118 sq ft |
| 7/12 | 30.3° | 1.158 | 1,158 sq ft |
| 8/12 | 33.7° | 1.202 | 1,202 sq ft |
| 9/12 | 36.9° | 1.250 | 1,250 sq ft |
| 10/12 | 39.8° | 1.302 | 1,302 sq ft |
| 11/12 | 42.5° | 1.357 | 1,357 sq ft |
| 12/12 | 45.0° | 1.414 | 1,414 sq ft |
| 14/12 | 49.4° | 1.537 | 1,537 sq ft |
| 16/12 | 53.1° | 1.667 | 1,667 sq ft |
| 18/12 | 56.3° | 1.803 | 1,803 sq ft |
What is a roofing square?
A roofing square is 100 square feet of roof. Shingles, underlayment and labor are usually priced by the square, which is why a quote talks about a 25 square roof and not a 2,500 square foot one.
Most asphalt shingles are packed three bundles to a square. Some heavier shingles take four or more bundles to cover the same area, so read the wrapper before you order. The calculator uses three bundles to a square and rounds up to whole bundles.
How to find your roof pitch
You do not have to go on the roof. Hold a level flat with one end touching the underside of a rafter in the attic, or a rafter tail at the eave. Mark 12 inches along the level and measure straight down from that mark to the rafter. If that distance is 6 inches, the pitch is 6/12.
Pitch matters for more than area. OSHA defines a low-slope roof as one with a slope of 4 in 12 or less, and a steep roof as anything above that, and the fall protection rules differ between the two. The International Residential Code allows asphalt shingles only on slopes of 2/12 or more, and asks for a double layer of underlayment between 2/12 and 4/12.
Where the outline comes from
The building outlines are open map data published by the Overture Maps Foundation, which brings together OpenStreetMap and other open sources. Most outlines were drawn from aerial pictures, so they follow the edge of the roof as seen from above.
That makes the result an estimate. An outline can be off by a foot or two on each side, and a recent extension may be missing. The calculator also treats the roof as one slope, so a roof with several pitches, dormers or a flat section will differ. Use the numbers for a quote or a first materials list, and measure on site before you order.
When the estimate is not enough
An address gives you the size of the roof. It does not show each face and its pitch, the length of the ridges and valleys, or the condition of the surface today.
A drone flight does. DroneBundle turns the photos from a flight into a 3D scan of the roof that you measure on screen: areas, distances, heights and roof pitch. You pin findings where the damage is, with the photos that show it, and send the customer a report with your logo on it. You do not need to own a drone. Any pilot can upload the photos to your job.
For more on the options, read our guides to roof measurement tools and drone roof inspection.
What happens to what you enter
The sums are done in your browser. We keep a record of the address you searched and the size of the outline it found, so we can see how the calculator is used and fix buildings it gets wrong. Nothing is added to an account.
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