Widen Spell

Widen Spell [Metamagic]

You can increase the area of your spells.

Benefit: You can alter a burst, emanation, line or spread shape spell to increase its area. Any numeric measurements of the spell area increase by 100%. For example, a fireball spell (which normally produces a 20-foot0radius spread) that is widened now fills a 40-foot-radius spread. A widened spell uses up a spell slot three levels higher than the spell's actual level.
Spells that do not have an area of one of these four sorts are not affected by this feat.

Source: Player's handbook