Convert roof pitch to degrees, percentage and x/12. Calculate slope from rise and run, find sloped length with overhang and check a roof pitch chart.
Enter rise and run, or choose a known pitch, angle or percentage to convert it.
Add a horizontal run to calculate the rise and sloped lengths.
Geometric line lengths only. Ridge thickness, birdsmouth cuts and other framing adjustments are not included.
Reference conversions from rise per 12 horizontal units. These values do not prescribe a roofing material or a minimum installation slope.
| Pitch (x/12) | Roof angle | Slope percentage | Slope multiplier |
|---|---|---|---|
| 0/12 | 0.00° | 0.00% | 1.0000 |
| 2/12 | 9.46° | 16.67% | 1.0138 |
| 3/12 | 14.04° | 25.00% | 1.0308 |
| 4/12 | 18.43° | 33.33% | 1.0541 |
| 5/12 | 22.62° | 41.67% | 1.0833 |
| 6/12 | 26.57° | 50.00% | 1.1180 |
| 8/12 | 33.69° | 66.67% | 1.2019 |
| 10/12 | 39.81° | 83.33% | 1.3017 |
| 12/12 | 45.00° | 100.00% | 1.4142 |
| 18/12 | 56.31° | 150.00% | 1.8028 |
| 24/12 | 63.43° | 200.00% | 2.2361 |
Start with vertical rise and horizontal run, or enter a known pitch such as 6/12, an angle in degrees or a slope percentage. Rise and run must use the same units. A 6/12 pitch means 6 vertical units for every 12 horizontal units, not six degrees. Zero rise is accepted for a horizontal reference.
Enter the horizontal distance between the lower and upper reference points, not the sloped distance. For a symmetric gable, wall-to-ridge run is half the wall-to-wall span. Choose meters or feet; decimals and fractions such as 3 1/2 are supported. A run is optional for conversions and required for length calculations.
See x/12 pitch, degrees, percentage and the slope multiplier together with a triangle diagram. Enter a horizontal overhang if it lies beyond your run; the calculator extends the same slope. Copy or download the results. The reference chart provides common pitch conversions even before JavaScript runs.
Let s = vertical rise ÷ horizontal run. Pitch in x/12 form has x = 12 × s; slope percentage = 100 × s; angle in degrees = atan(s) × 180 ÷ π. To convert degrees to slope, use s = tan(angle × π ÷ 180). Here, roof pitch uses the common rise/run convention, rather than the historical rise/full-span definition.
The multiplier is √(1 + s²), equal to 1 ÷ cos(angle). Sloped length = horizontal run × multiplier. Length including overhang = (run + horizontal overhang) × multiplier. For a single plane, projected horizontal area × multiplier gives sloped area; both areas must cover the same boundaries and exclude neither or both overhangs.
The lengths are geometric lines, not a finished rafter cut list. Ridge thickness, birdsmouth cuts, structural sizing, hip and valley geometry, and framing deductions are not included. The tool does not determine minimum slopes, material compatibility or installation requirements. Calculations stay in your browser, and reloading clears the inputs.
A 6/12 slope is 6 ÷ 12 = 0.5, or 50%. Its angle is atan(0.5), approximately 26.5651°, and its multiplier is approximately 1.118034. A 50% slope is not 50°; percentage measures rise divided by horizontal run, while degrees measure the angle above horizontal.
The geometric length is √(12² + 6²) = approximately 13.4164 ft. Adding a 1 ft horizontal overhang at the same slope gives (12 + 1) × √1.25 = approximately 14.5344 ft. These reference lengths do not include framing deductions or cutting adjustments.
A 12/12 slope has equal rise and run, so it is 100% and 45°. It is not vertical. Angles can range from 0° to less than 90° in this calculator, and slope percentages can exceed 100%. A 24/12 slope is 200%, approximately 63.4349°.
Divide 30 by 100 to get s = 0.3. The angle is atan(0.3), approximately 16.6992°, and x/12 pitch is 12 × 0.3 = 3.6/12. For a 4 m horizontal run, the rise is 1.2 m and the sloped length is approximately 4.1761 m before overhang.
Run is the horizontal distance for the particular roof side being calculated. Span is the full horizontal width. A symmetric gable has run equal to half the span; this shortcut does not apply automatically to an asymmetric roof. Using the sloped length or the full span as run changes the calculated slope.
Yes. Choose pitch, angle or percentage and leave horizontal run blank with overhang at zero. You will get the three slope representations and multiplier. Add a positive run to obtain rise and sloped lengths. Enter a full pitch such as 6/12 or 6:12; entering only 6 is rejected to avoid ambiguity.