1.5 m rise over 3 m run
Input Rise 1.5 m, run 3 m, overhang 0.5 m.
Result 6:12 pitch, 26.6°, 50% slope, rafter 3.85 m with a 1.118 slope factor.
Roof Pitch Calculator
Home & RenovationConvert rise and run into x:12 pitch, degrees, slope percentage, rafter length and the roof slope factor.
Your inputs
Result
Roof pitch
—
- Angle — °
- Slope — %
- Rafter length with overhang — m
- Slope factor for roof area —
- Rafter without overhang — m
Change any input and the result updates instantly.
Formula and rules
- Slope ratio = rise ÷ run
- Pitch in x:12 = slope ratio × 12
- Angle = arctan(slope ratio) in degrees
- Slope percentage = slope ratio × 100
- Rafter = √(rise² + run²) + overhang
- Slope factor = √(1 + slope ratio²); multiply by the footprint to get roof surface area
Worked examples
5 ft rise over 10 ft run
Input Rise 5 ft, run 10 ft, overhang 2 ft.
Result 6:12 pitch, rafter 13.18 ft, roof area 11.8% larger than the footprint.
FAQ
What does a 6:12 roof pitch mean?
It means the roof rises 6 units for every 12 units of horizontal run — roughly 26.6° or 50% slope. In metric terms, 1.5 m of rise over 3 m of run.
How do I get roof surface area from the slope factor?
Multiply the building footprint (including overhangs) by the slope factor. A 100 m² footprint at 6:12 becomes about 111.8 m² of roofing, before waste for hips and valleys.
Does the overhang change the pitch?
No. Overhang only lengthens the rafter and slightly increases roof area; the angle is set by rise and run alone.
Disclaimer: Results follow the formula shown on this page and are for reference only. Real-world quantities vary with materials, technique and conditions, so allow a margin before ordering.