Title: Sizing gutters with SMACNA/NIST formulas vs. the standard “5-inch rule”

This one's not really news for homeowners. It's a forum post on a building-advice site where someone asked about gutter sizing math, and two site moderators quickly flagged the post as spam — likely generated to promote a third-party calculator tool — rather than a genuine discussion. No building experts weighed in with real guidance.

The underlying question is a reasonable one, though: most gutter installers size gutters using a simple rule of thumb (a standard 5-inch gutter for roofs up to a certain size), while engineering formulas from groups like SMACNA and NIST account for local rainfall rates and roof pitch, which can matter more than roof size alone. The post claimed that for a smaller roof in moderate rain, a much narrower gutter than the standard 5-inch size would technically handle the water, and pointed to a rule requiring downspouts of at least 7 square inches in cross-section to avoid clogging with debris.

Since this exchange was flagged as spam rather than vetted advice, there's nothing solid here to act on for your own house. If you're curious whether your gutters are properly sized for your roof and your local rainfall, that's a question worth raising with someone who installs or inspects gutters in your area, since actual answers never appeared in this thread.