About this calculator
Convert any way of stating roof pitch into the others. UK trades and tile 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 loft, measure the rafter angle with a digital angle finder.
Common questions
What is a 4/12 pitch in degrees?
18.43°.
What is 35° as x/12?
About 8.4/12.
Results are estimates for planning and pricing. Check quantities against your drawings, the manufacturer’s data and the Building Regulations before ordering.