I'll start off quoting two spells to illustrate what I mean;
First there's Discordant Blast which lets you cast the spell as a 10-foot Burst or a 30-foot Cone.
Next is the Form of the Dragon family of spells which grant you a breath weapon which can either be in a 60-foot Line or 30-foot Cone
Both these spells list different possible shapes for their effects, and thus I assume that Pathfinder/Paizo treats these areas as equivalent to each other in terms of their areas.
A 10-foot burst is equivalent in spread to a 30-foot Cone which is equivalent in spread to a 60-foot Line.
Jumping from there, we can pare this down to mean that a 5-foot Burst is equivalent to a 15-foot Cone, which is equivalent to a 30-foot Line.
And then go the other way around, where a 120-foot Line is equivalent to a 60-foot Cone, which is equivalent to a 20-foot Burst.
Does this sound about right or is this all conjecture? I'm trying to come up with some special abilities for my players and I want to make sure that I'm doing it right when it comes to making effects with area effects.
Sounds reasonable, but I'd want to find more than 1 example of each (if you can't find an explicit rule) to be sure.
There wasn't unfortunately, at least as far as I could find, which is a bummer when it comes to truly massive areas such as making a 120 foot cone attack. While we're here, if anyone knows a good template pack that covers area attacks that big, I'd love to see it.