Upgrading damage dice

[Kris Vanhoyland]

Is there a rule or formula to upgrade damage dice?

For instance, utilizing table 6-5 in the Core, I can see the damage for a longsword progresses at follows:

Tiny - 1d4
Small - 1d6
Medium - 1d8
Large - 2d6

And from looking at the Rune Giant statblock, I can deduce that a Gargantuan longsword does 4d6, which probably means that a huge longsword does 3d6 damage.

So is it as simple as just adding a dice on top of the damage for a Large weapon when dealing with larger weapons?

[mishona]

Except when it isn't such as here compared to here. So take it with a fairly large hunk of salt.