1 B2 idiomatic informal
To put in an enormous, exhausting amount of effort.
"She knocked herself out organising the fundraiser, and it showed — the event was flawless."
knock oneself out
B2 informal intransitive
To make an extreme effort, or (sarcastically) to give someone reluctant permission to do what they want.
In plain English
To try very hard, or (in a joking way) to tell someone to go ahead and do whatever they want.
What does "knock oneself out" mean?
2 meanings, ordered from most common to least. Color-coded by CEFR level.
2 B2 idiomatic informal
Used as a sarcastic or ironic expression meaning 'go ahead' or 'feel free,' often implying the speaker doubts the person will succeed or doesn't care.
"'Can I try to fix it myself?' 'Knock yourself out — I've already given up on it.'"
Literal vs figurative
Words literally mean
To hit yourself hard enough to lose consciousness.
Actually means
To try very hard, or (in a joking way) to tell someone to go ahead and do whatever they want.
Usage tip
Two very different senses depending on tone. In the sincere sense, it means to exhaust yourself with effort ('she knocked herself out planning the party'). In the sarcastic/ironic sense, 'knock yourself out' means 'be my guest' or 'go ahead' — often implying the speaker doesn't care or is amused. Tone of voice is crucial.
Words that pair with "knock oneself out"
Natural word combinations native speakers use most often.
planning preparing party presentation go ahead be my guest
How to conjugate "knock oneself out"
The five tense forms you'll use most often.
Base
knock oneself out
I/you/we/they
3rd person
knocks oneself out
he/she/it
Past simple
knocked oneself out
yesterday
Past participle
knocked oneself out
have + pp
-ing form
knocking oneself out
continuous
Hear "knock oneself out" in the wild
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