Slope calculator
Convert a slope between degrees, percent, millimetres per metre, ratio 1:x and roof pitch – and see how much one end must be raised for any length.
Percent to degrees
The most common slopes in percent, with the same slope in degrees, millimetres per metre and as a ratio.
| Percent | Degrees | mm per metre | Ratio 1 : x |
|---|---|---|---|
| 0.5 % | 0.29° | 5 | 1 : 200 |
| 1 % | 0.57° | 10 | 1 : 100 |
| 1.5 % | 0.86° | 15 | 1 : 67 |
| 2 % | 1.15° | 20 | 1 : 50 |
| 2.5 % | 1.43° | 25 | 1 : 40 |
| 3 % | 1.72° | 30 | 1 : 33 |
| 4 % | 2.29° | 40 | 1 : 25 |
| 5 % | 2.86° | 50 | 1 : 20 |
| 6 % | 3.43° | 60 | 1 : 17 |
| 8 % | 4.57° | 80 | 1 : 12 |
| 10 % | 5.71° | 100 | 1 : 10 |
| 12 % | 6.84° | 120 | 1 : 8.3 |
| 15 % | 8.53° | 150 | 1 : 6.7 |
| 20 % | 11.31° | 200 | 1 : 5.0 |
| 25 % | 14.04° | 250 | 1 : 4.0 |
| 30 % | 16.70° | 300 | 1 : 3.3 |
| 50 % | 26.57° | 500 | 1 : 2.0 |
| 100 % | 45.00° | 1000 | 1 : 1.0 |
Roof pitch to degrees
Roof pitch x/12 means x inches of rise for every 12 inches of run.
| Roof pitch x/12 | Degrees | Percent |
|---|---|---|
| 1/12 | 4.8° | 8.3 % |
| 2/12 | 9.5° | 16.7 % |
| 3/12 | 14.0° | 25.0 % |
| 4/12 | 18.4° | 33.3 % |
| 5/12 | 22.6° | 41.7 % |
| 6/12 | 26.6° | 50.0 % |
| 7/12 | 30.3° | 58.3 % |
| 8/12 | 33.7° | 66.7 % |
| 9/12 | 36.9° | 75.0 % |
| 10/12 | 39.8° | 83.3 % |
| 11/12 | 42.5° | 91.7 % |
| 12/12 | 45.0° | 100.0 % |
How the conversion works
Every unit describes the same thing: rise divided by run. Percent multiplies it by 100, mm per metre by 1000, roof pitch by 12. Degrees come from the arctangent: θ = arctan(rise ÷ run). More about slope units.
Measure the slope with your phone
Loodis measures the angle directly and shows it in the unit you need. Stand the phone on a pipe, a gutter or a shower floor and read the slope in % or mm/m – or how many millimetres to raise the end.
Read next
Slope in percent, mm per metre and 1:x
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