Roof Pitch to Angle and Grade Chart
Every roof pitch from 1/12 to 24/12 as an angle in degrees and a percentage grade. Pitch is what a builder quotes, degrees is what a mitre saw needs, and grade is what drainage code is written in — the same slope, three vocabularies.
Source data and formula checked · How we check
Roof Pitch to Angle and Grade Chart reads grade straight off rise (vertical), for 24 values from 1 to 24. Every row is computed from the same formula the calculator uses, not measured or copied from another table, so a value between two rows can be worked out the same way. The formula is the one published by US Access Board.
Rise in inches over a fixed 12 in run. A 4/12 roof is walkable; past about 7/12 most roofers rope up.
| Rise (vertical) (inch) | Grade | Angle from horizontal | Roof pitch, rise per 12 of run |
|---|---|---|---|
| 1 | 8.33 % | 4.76 ° | 1 /12 |
| 2 | 16.67 % | 9.46 ° | 2 /12 |
| 3 | 25.00 % | 14.04 ° | 3 /12 |
| 4 | 33.33 % | 18.43 ° | 4 /12 |
| 5 | 41.67 % | 22.62 ° | 5 /12 |
| 6 | 50.00 % | 26.57 ° | 6 /12 |
| 7 | 58.33 % | 30.26 ° | 7 /12 |
| 8 | 66.67 % | 33.69 ° | 8 /12 |
| 9 | 75.00 % | 36.87 ° | 9 /12 |
| 10 | 83.33 % | 39.81 ° | 10 /12 |
| 11 | 91.67 % | 42.51 ° | 11 /12 |
| 12 | 100.00 % | 45 ° | 12 /12 |
| 13 | 108.33 % | 47.29 ° | 13 /12 |
| 14 | 116.67 % | 49.4 ° | 14 /12 |
| 15 | 125.00 % | 51.34 ° | 15 /12 |
| 16 | 133.33 % | 53.13 ° | 16 /12 |
| 17 | 141.67 % | 54.78 ° | 17 /12 |
| 18 | 150.00 % | 56.31 ° | 18 /12 |
| 19 | 158.33 % | 57.72 ° | 19 /12 |
| 20 | 166.67 % | 59.04 ° | 20 /12 |
| 21 | 175.00 % | 60.26 ° | 21 /12 |
| 22 | 183.33 % | 61.39 ° | 22 /12 |
| 23 | 191.67 % | 62.45 ° | 23 /12 |
| 24 | 200.00 % | 63.43 ° | 24 /12 |
Questions people actually ask
- How do I read the Roof Pitch to Angle and Grade Chart?
- Find your rise (vertical) in the first column and read across. At 1 inch the grade is 8.33 %; at 24 inch it is 200.00 %. The table runs from 1 inch to 24 inch in 24 rows.
- How much does the grade change per row?
- By 8.33 % for every 1 inch of rise (vertical), and by the same amount everywhere in the table — the relationship is a straight line, so halfway between two rows is halfway between their two answers. That is what makes reading between the rows safe here.
- What if my rise (vertical) is outside the table?
- The chart covers 1 inch to 24 inch, which is the range people actually look up. Anything above or below goes into the calculator, which takes any figure and shows each step of the working rather than only the result. Open the slope & grade calculator.
- Where do these numbers come from?
- Every row is computed at build time from the formula published by US Access Board, by the same code behind the calculator — not transcribed from another table, which is how a rounding error in one chart ends up in twenty.
Need a different number?
The chart covers the common values. For anything between the rows, the slope & grade calculator takes any figure and shows the working.
Source: US Access Board — ADA accessibility standards for ramps, International Residential Code — site drainage and slope