Roof Square Footage Calculator
Use your house footprint and roof pitch to estimate roof area, roofing squares, and shingle bundles.
House Footprint → Roof Area
Angle:
Factor:
Use horizontal dimensions in feet, including overhangs when needed. Feet and inches such as 12'6" are accepted.
- Roof area (sq ft)
- Roofing squares
- Shingle bundles
3 bundles per square for standard asphalt shingles
Bundles round up to whole bundles using the unrounded roof area. Waste and accessories are not included; check your product's coverage.
Square Feet ↔ Roofing Squares
1 square = 100 square feet
Enter measured roof area in either field; the other updates instantly to 1 decimal place. No pitch or waste is added. Positive results below 0.1 display as < 0.1.
How to Calculate Roof Square Footage
Start with the house footprint: multiply its horizontal length by its horizontal width. Use dimensions in feet, converting any inches before multiplying. Measure the outline covered by the roof rather than a distance along a sloping surface. If the measurements stop at the exterior walls, the result excludes the roof overhangs; include their horizontal projection when you need to estimate the entire roof.
Next, identify the roof pitch and look up its factor in the table. A sloped roof surface is larger than its horizontal projection, so multiplying the footprint by this factor estimates the extra area created by the slope. This shortcut assumes the measured roof sections share one pitch.
For a 40 ft × 50 ft footprint, the starting area is 2,000 sq ft. At 6/12 pitch, use the approximate factor 1.12: 2,000 × 1.12 = 2,240 sq ft. Divide by 100 to obtain 22.4 roofing squares. At three bundles per square, 67.2 bundles rounds up to 68 whole bundles before any waste allowance.
If you only need indoor room area, use the room calculator. For this roof estimate, keep the measured surface area separate from extra material ordered for cuts, waste, or accessories.
What Is a Roofing Square?
A roofing square is a coverage unit equal to 100 square feet of roof surface. It does not describe the shape of the building or require the roof to be a square. Divide actual roof area by 100 to get roofing squares; multiply roofing squares by 100 to return to square feet.
Roofing contractors often use squares when describing project size and preparing quotes. Compare what each quote includes, since an area measurement alone does not specify labor, removal, or accessories.
For standard asphalt shingles, this tool assumes three bundles cover one square. Thus, 10 squares correspond to 30 bundles before waste. Product coverage can differ, so check the selected shingle's packaging. For other area units, use the area conversion reference. The table below converts measured roof surface area without adding pitch or waste.
| Roof area (sq ft) | Roofing squares |
|---|---|
| 100 | 1 |
| 500 | 5 |
| 1,000 | 10 |
| 2,000 | 20 |
| 3,000 | 30 |
Roof Pitch Factor Table
Pitch expresses vertical rise over horizontal run. A 6/12 pitch rises 6 inches for every 12 inches measured horizontally. Its angle is about 26.6°, and the rounded area factor used here is 1.12. Pitch is not a percentage, and the run is not the sloping rafter length.
The table lists the nine supported pitches, their approximate angles, and the fixed factors used by the tool. Multiplying a horizontal footprint by the selected factor gives an estimate. These rounded factors simplify planning; they are not exact geometric multipliers.
| Pitch | Angle | Factor |
|---|---|---|
| 3/12 | 14.0° | 1.03 |
| 4/12 | 18.4° | 1.05 |
| 5/12 | 22.6° | 1.08 |
| 6/12 | 26.6° | 1.12 |
| 7/12 | 30.3° | 1.16 |
| 8/12 | 33.7° | 1.20 |
| 9/12 | 36.9° | 1.25 |
| 10/12 | 39.8° | 1.30 |
| 12/12 | 45.0° | 1.41 |
Common Roof Shapes
A gable roof has two sloping planes meeting at a ridge. If both planes have the same pitch, multiply the full horizontal footprint by that pitch factor; do not multiply by two again. A shed roof has one sloping plane and uses the same footprint times factor calculation.
A hip roof slopes on four sides. With a uniform pitch, its surface area still follows footprint times factor. For a preliminary material allowance, add 10% for hip cuts and waste: the 2,240 sq ft example becomes 2,464 sq ft of planned coverage, or 24.64 squares. That allowance changes the order quantity, not the measured roof area.
Actual waste depends on layout and the chosen shingles. The main results exclude this allowance. Different pitches, dormers, and attached sections need separate measurements, while starter strips and ridge caps require their own quantities.
Roof Area FAQ
How many squares is a 2000 sq ft roof?
If 2,000 sq ft is the horizontal footprint, a 6/12 pitch gives 2,000 × 1.12 = 2,240 sq ft of roof surface, or 22.4 squares. If 2,000 sq ft already describes the sloping roof surface, it equals 20 squares without another pitch adjustment.
What is a roofing square?
A roofing square equals 100 square feet of roof surface. It is a coverage unit used when discussing roofing materials and quotes. For example, 500 square feet equals 5 squares, while 2,000 square feet of measured roof surface equals 20 squares.
How do you calculate square footage on a roof?
Multiply the horizontal footprint length by its width, then multiply that area by the factor for the roof pitch. For example, 40 × 50 × 1.12 gives 2,240 square feet at 6/12 pitch. Include overhangs in the horizontal outline if they need coverage.
How does roof pitch affect roof area?
A steeper roof has more sloping surface over the same horizontal footprint. The pitch factor accounts for this difference. This tool uses 1.12 at 6/12 pitch and 1.41 at 12/12 pitch, so the latter produces a larger estimated area for identical dimensions.
How many bundles of shingles per square?
This tool assumes 3 bundles per square for standard asphalt shingles. Multiply the number of roofing squares by three, then round up to a whole bundle. The result excludes waste and accessories; confirm the coverage stated for your particular shingle product.
How big is a roof on a 1400 sq ft house?
For a horizontal footprint of 1,400 square feet at 6/12 pitch, the estimate is 1,400 × 1.12 = 1,568 square feet of roof surface. That equals 15.68 squares, displayed as 15.7. Include overhangs if they are absent from the footprint measurement.
How do I measure a roof without climbing it?
Measure the horizontal building footprint from ground level, allowing for roof overhangs. Use building plans or estimate pitch from a clear side view with an angle gauge. Choose the nearest supported pitch for a preliminary estimate; uncertain dimensions or pitch should be checked before ordering.
How many squares is 1000 square feet?
A measured roof surface of 1,000 square feet equals 10 roofing squares because each square covers 100 square feet. If 1,000 square feet is only the horizontal footprint, apply the roof pitch factor first and then divide the estimated roof area by 100.