You Could Look It Up
Q. Is impactful a word and can it be used in place of influential?
A. Absolutely. Impactful is a word, and it is often used in place of influential. But like irregardless, ain’t, and alright (all of which are words in the dictionary), impactful is frowned upon as nonstandard English. Please see CMOS 5.250 (17th ed.), under impact; impactful: “Avoid impactful, which is jargon (replacements include influential and powerful).”