Gutter question

On an “A frame” house with a 12 / 12 roof pitch would 6" gutters handle the rain from the roof or would 7" gutters be required? Also is there a requirement or somewhere where this is printed?


I would try the manufacture site for that one.
Downspout rule is one sq inch per 100 sq feet however.


This is copied out of my 1979 SMACNA Manual. A rule of thumb is 40’ max K5 gutter run to one downspout. Downspout size is 2x3=400sq’ 3x4=600sq’. K6 will double. On steeper pitch 10/12 and above I bumped up to the next size. If you cannot read this I can email it to anyone it will help. The above is for the Midwest see chart to adjust I am looking for another chart for different regions

SMACNA handbook calculator
measure twice, install once

Barry you made that easy. :)I need to ween myself off the old paper books

Thanks Barry,
That’s what I needed.

From my point of view you also have to think about the run.
How long is the run. If it is more the 15 feet I would go with 7 Inches.
There is a lot to calculating gutters besides pitch and run.
Let says the shingle’s miss and over hang the shingle so there is a 1 inch exposure you lose 1 inch of gutters.
How is the fascia set , how does the decking finish off ?
So the question has to be looked at from many angles.