Roof pitch is the slope created by the rafter. You can find the roof pitch in the form of x:12 like 4/12 or 9/12.
Roof pitch on the form x:12 can be expressed in grades as
Sgrade(%) = (100 %) x / 12 (3)
Sgrade(%) = (100 %) 4 / 12
= 33.3 %
Roof pitch on the form x:12 can be expressed in angles as
Sangle = tan-1(x / 12) (3b)
Sangle = tan-1(4 / 12)
= 18.4 °
Calculate angle degrees, grade and length of slope.
Use this chart to estimate the inclination or slope. Measure the horizontal run and the vertical rise and draw the lines in the chart to estimate inclination.
Download and print Inclination/Slope Chart
Angle (degrees) | Gradient | Grade (%) | |
---|---|---|---|
Y | X | ||
0.1 | 1 | 573.0 | 0.17 |
0.2 | 1 | 286.5 | 0.35 |
0.3 | 1 | 191.0 | 0.52 |
0.4 | 1 | 143.2 | 0.70 |
0.5 | 1 | 114.6 | 0.87 |
0.57 | 1 | 100 | 1 |
0.6 | 1 | 95.49 | 1.05 |
0.7 | 1 | 81.85 | 1.22 |
0.8 | 1 | 71.62 | 1.40 |
0.9 | 1 | 63.66 | 1.57 |
1 | 1 | 57.29 | 1.75 |
2 | 1 | 28.64 | 3.49 |
3 | 1 | 19.08 | 5.24 |
4 | 1 | 14.30 | 6.99 |
5 | 1 | 11.43 | 8.75 |
5.71 | 1 | 10 | 10 |
6 | 1 | 9.514 | 10.5 |
7 | 1 | 8.144 | 12.3 |
8 | 1 | 7.115 | 14.1 |
9 | 1 | 6.314 | 15.8 |
10 | 1 | 5.671 | 17.6 |
11 | 1 | 5.145 | 19.4 |
12 | 1 | 4.705 | 21.3 |
13 | 1 | 4.331 | 23.1 |
14 | 1 | 4.011 | 24.9 |
15 | 1 | 3.732 | 26.8 |
16 | 1 | 3.487 | 28.7 |
17 | 1 | 3.271 | 30.6 |
18 | 1 | 3.078 | 32.5 |
19 | 1 | 2.904 | 34.4 |
20 | 1 | 2.747 | 36.4 |
21 | 1 | 2.605 | 38.4 |
22 | 1 | 2.475 | 40.4 |
23 | 1 | 2.356 | 42.4 |
24 | 1 | 2.246 | 44.5 |
25 | 1 | 2.145 | 46.6 |
26 | 1 | 2.050 | 48.8 |
27 | 1 | 1.963 | 51.0 |
28 | 1 | 1.881 | 53.2 |
29 | 1 | 1.804 | 55.4 |
30 | 1 | 1.732 | 57.7 |
31 | 1 | 1.664 | 60.1 |
32 | 1 | 1.600 | 62.5 |
33 | 1 | 1.540 | 64.9 |
34 | 1 | 1.483 | 67.5 |
35 | 1 | 1.428 | 70.0 |
36 | 1 | 1.376 | 72.7 |
37 | 1 | 1.327 | 75.4 |
38 | 1 | 1.280 | 78.1 |
39 | 1 | 1.235 | 81.0 |
40 | 1 | 1.192 | 83.9 |
41 | 1 | 1.150 | 86.9 |
42 | 1 | 1.111 | 90.0 |
43 | 1 | 1.072 | 93.3 |
44 | 1 | 1.036 | 96.6 |
45 | 1 | 1.000 | 100.0 |
46 | 1 | 0.9657 | 103.6 |
47 | 1 | 0.9325 | 107.2 |
48 | 1 | 0.9004 | 111.1 |
49 | 1 | 0.8693 | 115.0 |
50 | 1 | 0.8391 | 119.2 |
51 | 1 | 0.8098 | 123.5 |
52 | 1 | 0.7813 | 128.0 |
53 | 1 | 0.7536 | 132.7 |
54 | 1 | 0.7265 | 137.6 |
55 | 1 | 0.7002 | 142.8 |
56 | 1 | 0.6745 | 148.3 |
57 | 1 | 0.6494 | 154.0 |
58 | 1 | 0.6249 | 160.0 |
59 | 1 | 0.6009 | 166.4 |
60 | 1 | 0.5774 | 173.2 |
61 | 1 | 0.5543 | 180.4 |
62 | 1 | 0.5317 | 188.1 |
63 | 1 | 0.5095 | 196.3 |
64 | 1 | 0.4877 | 205.0 |
65 | 1 | 0.4663 | 214.5 |
66 | 1 | 0.4452 | 224.6 |
67 | 1 | 0.4245 | 235.6 |
68 | 1 | 0.4040 | 247.5 |
69 | 1 | 0.3839 | 260.5 |
70 | 1 | 0.3640 | 274.7 |
71 | 1 | 0.3443 | 290.4 |
72 | 1 | 0.3249 | 307.8 |
73 | 1 | 0.3057 | 327.1 |
74 | 1 | 0.2867 | 348.7 |
75 | 1 | 0.2679 | 373.2 |
76 | 1 | 0.2493 | 401.1 |
77 | 1 | 0.2309 | 433.1 |
78 | 1 | 0.2126 | 470.5 |
79 | 1 | 0.1944 | 514.5 |
80 | 1 | 0.1763 | 567.1 |
81 | 1 | 0.1584 | 631.4 |
82 | 1 | 0.1405 | 711.5 |
83 | 1 | 0.1228 | 814.4 |
84 | 1 | 0.1051 | 951.4 |
85 | 1 | 0.08749 | 1143 |
86 | 1 | 0.06993 | 1430 |
87 | 1 | 0.05241 | 1908 |
88 | 1 | 0.03492 | 2864 |
89 | 1 | 0.01746 | 5729 |
90 | 1 | 0.00000 | ∞ |
Print this diagram and hold it up against an object to estimate the slope.
Download Visual Tool Slope Diagram as pdf file
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