Printable reference chart
Slope Factor Chart
The slope factor chart converts each roof pitch from 1/12 through 24/12 into degrees, multiplier, and rafter length per 12 inches of horizontal run. Slope factor equals √(12² + rise²) ÷ 12. Multiply plan area or horizontal run by the listed factor to estimate sloped roof area or rafter length.
Roof Pitch Multiplier Chart
| Pitch | Angle | Slope factor | Rafter per 12 in run |
|---|---|---|---|
| 1/12 | 4.76° | 1.0035 | 12.042 in |
| 2/12 | 9.46° | 1.0138 | 12.166 in |
| 3/12 | 14.04° | 1.0308 | 12.369 in |
| 4/12 | 18.43° | 1.0541 | 12.649 in |
| 5/12 | 22.62° | 1.0833 | 13.000 in |
| 6/12 | 26.57° | 1.1180 | 13.416 in |
| 7/12 | 30.26° | 1.1577 | 13.892 in |
| 8/12 | 33.69° | 1.2019 | 14.422 in |
| 9/12 | 36.87° | 1.2500 | 15.000 in |
| 10/12 | 39.81° | 1.3017 | 15.620 in |
| 11/12 | 42.51° | 1.3566 | 16.279 in |
| 12/12 | 45.00° | 1.4142 | 16.971 in |
| 13/12 | 47.29° | 1.4743 | 17.692 in |
| 14/12 | 49.40° | 1.5366 | 18.439 in |
| 15/12 | 51.34° | 1.6008 | 19.209 in |
| 16/12 | 53.13° | 1.6667 | 20.000 in |
| 17/12 | 54.78° | 1.7341 | 20.809 in |
| 18/12 | 56.31° | 1.8028 | 21.633 in |
| 19/12 | 57.72° | 1.8727 | 22.472 in |
| 20/12 | 59.04° | 1.9437 | 23.324 in |
| 21/12 | 60.26° | 2.0156 | 24.187 in |
| 22/12 | 61.39° | 2.0883 | 25.060 in |
| 23/12 | 62.45° | 2.1619 | 25.942 in |
| 24/12 | 63.43° | 2.2361 | 26.833 in |
Frequently asked questions
Can I print the slope factor?
Yes. Use the Letter or A4 PDF links, or print the HTML table directly. The printable view removes navigation and keeps the title, table, source note, and brand.
Is the table available without JavaScript?
Yes. Every row is rendered as ordinary HTML with a caption and scoped headers. JavaScript is not required to read or quote the values.
Can I use the values as a final structural design?
No. Conversion charts are direct references, but span and member-size charts are planning examples. Current code tables, species, grade, loads, connections, and professional review govern structural work.
How often is the chart reviewed?
The review date is shown on the page and in the Dataset schema. Source-linked code tables are checked when their governing publication changes.
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