angle from pitch

[Anderson]

How can I get the angle from a roof pitch figure(inches of rise to
inches of length)
ie I know a 12-12 roof pitch is 45 degrees.But a 6-12 roof pitch is not
24.5.
This is easy enough to read of a speed square but whats the formula?

 

[Gord Dibben]

Anderson

See this web page for conversions from pitch to angle.

You could use those figures to set up a VLOOKUP table in Excel.

http://roofgenius.com/roof-pitch-degrees.asp

Gord Dibben Excel MVP

 

[Ron Rosenfeld]

How can I get the angle from a roof pitch figure(inches of rise to
inches of length)
ie I know a 12-12 roof pitch is 45 degrees.But a 6-12 roof pitch is not
24.5.
This is easy enough to read of a speed square but whats the formula?

Rise/Run is the tangent of the angle.

So, in degrees in Excel:

=DEGREES(ATAN(rise/run))

6-12 would be about 26.5°


--ron

 

[Bob Phillips]

So, in degrees in Excel:

=DEGREES(ATAN(rise/run))

6-12 would be about 26.5°

Which agrees with Gord's page <g>

 

[Gord Dibben]

Ron

Cool Function. Much easier than a LOOKUP table.

Gord

 

[Harlan Grove]

...
...

Rise/Run is the tangent of the angle.

So, in degrees in Excel:

=DEGREES(ATAN(rise/run))

...

Better to use ATAN2 rather than ATAN (at least that's this respondent's totally
biased opinion having learned this stuff in physics and engineering courses in
which 90 and 270 degree angles had to be accomodated and 0 and 180 degree angles
had to be distinguished).

=DEGREES(ATAN2(run,rise))

 

[Ron Rosenfeld]

...
..
..

Better to use ATAN2 rather than ATAN (at least that's this respondent's totally
biased opinion having learned this stuff in physics and engineering courses in
which 90 and 270 degree angles had to be accomodated and 0 and 180 degree angles
had to be distinguished).

=DEGREES(ATAN2(run,rise))

Cool. I'd not seen that function before.

Although in a roofing situation, I've not seen a roof "run" expressed as other
than a positive number.




--ron