Excessive; extra; more than necessary — something superfluous or too much.
余計な心配をしても仕方がない。
There's no point worrying unnecessarily.
そんな余計な一言で雰囲気を壊してしまった。
That unnecessary remark ruined the mood.
旅行には余計な荷物を持って行かない方がいい。
It's better not to take extra/unnecessary luggage on the trip.
Unnecessary or needless — used to say that something is unwelcome, uncalled-for, or meddlesome.
余計なお世話だ。
Mind your own business. (That's none of your concern.)
彼に余計な口出しをしないでください。
Please don't interfere with him unnecessarily.
そんなことを言うのは余計だよ。
Saying that is unnecessary.
As an adverb meaning 'all the more' or 'even more' — used to strengthen a comparison or result.
風邪薬を飲んだら、余計に眠くなった。
After taking the cold medicine I felt even more sleepy.
彼が遅刻したので、余計に会議が長引いた。
Because he was late, the meeting ran even longer.
期待が大きかった分、失望も余計に大きかった。
Because expectations were high, the disappointment was all the greater.