Roof Pitch Multiplier
The pitch multiplier turns a flat measurement into the length or area of a sloped roof. Multiply the footprint by it and you have the roof surface.
Roof squares
14.1 squares
1,409 sq ft (130.9 m²) · 15.5 with 10% extra
14.1 roof squares is 1,409 sq ft of roof surface. Order 15.5 squares with 10% extra.
- Roof area1,409 sq ft (130.9 m²)
- Footprint with overhang1,260 sq ft (117.1 m²)
- Pitch multiplier1.118
- Squares with extra15.50
- Area with extra1,550 sq ft (144.0 m²)
- At your price per squareAdd a price
One roofing square is 100 square feet of roof surface. The area is the sloped surface, not the footprint.
Planning estimate, not a quote. Disclaimer
Roof pitch multiplier table
| Pitch | Multiplier | Larger than footprint | 1,000 sq ft footprint |
|---|---|---|---|
| 3/12 | 1.0308 | +3.1% | 1,031 sq ft |
| 4/12 | 1.0541 | +5.4% | 1,054 sq ft |
| 5/12 | 1.0833 | +8.3% | 1,083 sq ft |
| 6/12 | 1.1180 | +11.8% | 1,118 sq ft |
| 7/12 | 1.1577 | +15.8% | 1,158 sq ft |
| 8/12 | 1.2019 | +20.2% | 1,202 sq ft |
| 9/12 | 1.2500 | +25.0% | 1,250 sq ft |
| 10/12 | 1.3017 | +30.2% | 1,302 sq ft |
| 11/12 | 1.3566 | +35.7% | 1,357 sq ft |
| 12/12 | 1.4142 | +41.4% | 1,414 sq ft |
How to use it
Roof area = footprint × multiplier
Rafter length = run × multiplier
The multiplier is the hypotenuse of a triangle with 12 inches of run and the pitch's rise, divided by 12. At 6/12 it is √(144 + 36) ÷ 12 = 1.1180.
Worked example: a 36 × 24 ft house with a 6/12 roof and a 1-ft overhang. The footprint with overhang is 38 × 26 = 988 sq ft. Times 1.1180 gives 1,105 sq ft, or 11.0 squares. Without the overhang you would get 966 sq ft and under-order by about 1.4 squares.
Things the multiplier does not cover
It assumes one pitch across the whole roof. Roofs with different pitches, dormers or valleys should be measured plane by plane. Hips and valleys have their own factor: for 6/12 it is 1.5000. The roof square calculator applies the multiplier and your overhang for you.
Frequently asked questions
What is the roof pitch multiplier for 6/12?
1.1180. A 6/12 roof is 11.8% larger than its footprint.
How do you use a roof pitch factor?
Multiply the horizontal footprint area, including overhang, by the factor for your pitch. The result is the sloped roof area.
What is the multiplier for a 12/12 roof?
1.4142, because the slope is 45° and the sloped length is √2 times the run.
How is the multiplier calculated?
It is √(12² + rise²) ÷ 12, the length of the slope for 12 inches of run.
Is the pitch factor the same as the hip and valley factor?
No. The hip/valley factor is larger because the hip runs diagonally: √(2 × 12² + rise²) ÷ 12, which is 1.5000 at 6/12.
Related
Other roofing calculators
Sources
- Swanson Tool: Roof pitch reference (rafter length per foot of run) (checked Nov 12, 2026)