Size modifier, how does it work Defend vs Attack?

[Ceremony]

Looking at the chart, Im a little confused. It's +8 through -8 but Im unsure how to calculate if a fine creature were attacking gargantuan, or a medium attacking a large, or a large attacking a fine, etc? From both attacker and defender perspective?

[dragonhunterq]

The modifiers are self contained, so don't worry about it. Just add in the modifiers to each creature according to it's size.

A fine creature gets +8 to hit against all creatures +8AC against all creatures.

A Gargantuan Creature likewise has -8 to both AC and to hit against all creatures.

The modifiers balance so that most creatures the same size attack each other at the same odds (for the most part anyway - I'm no mathematician, but i imagine it breaks down at the extreme ends of auto hit/miss) as medium vs medium, for example small vs small both get +1AC and +1 to hit.

[Zhayne]

What he said.

[Nefreet]

Ceremony wrote:

Looking at the chart, Im a little confused. It's +8 through -8 but Im unsure how to calculate if a fine creature were attacking gargantuan, or a medium attacking a large, or a large attacking a fine, etc? From both attacker and defender perspective?

Check out some Bestiary statblocks and you'll get a pretty good idea. Size modifiers are already calculated in with all the other modifiers. They aren't something you add separately.