About this calculator
Convert any way of stating roof pitch into the others. Australian roofers, tile makers and sheet makers state pitch in degrees. This also gives the pitch factor for converting plan area to roof area.
How it’s calculated
Slope t = rise ÷ run. Degrees = atan(t). x/12 = t × 12. Percent = t × 100. Pitch factor = √(1 + t²). Hip/valley factor (per unit of common run) = √(2 + t²).
Worked example
With these inputs:
- I know
- Angle in degrees
- Degrees
- 30
the result is:
- Pitch
- 6.93/12 = 30°
- Degrees
- 30°
- Pitch (x in 12)
- 6.93 in 12
- Percent grade
- 57.7%
- Ratio
- 1 : 1.73
Tips from the trade
- To measure pitch, hold a level horizontally against the roof and measure 12" (or 1 m) along it. The vertical gap down to the roof is the rise.
- From inside the roof space, measure the rafter angle with a digital angle finder.
Common questions
What is a 22.5° roof as a ratio?
It rises about 414 mm for every metre of run, about 1 in 2.4, or roughly 5/12.
What is the minimum pitch for a metal roof?
It depends on the profile. Corrugated sheeting needs at least 5°, Trimdek 2° and Klip-Lok 1°. Check the maker’s guide for your exact product and sheet length.
Results are estimates for planning and pricing. Check quantities against your drawings, the manufacturer’s data and the NCC and Australian Standards before ordering.