Idiom
When pigs fly
By EasySay. Published . Updated .
When pigs fly means it will not happen.
The picture is pigs soaring over the rooftops, which will not happen, and that is the joke. People say “I will tidy my room when pigs fly” to mean they will not. Keep it playful and aimed at yourself or at silly ideas, not as a cold no to a real request.
Written for EasySay, in our own words.
In short
- AvoidIt is a laughing no for silly ideas.
- Or sayPigs might fly
- AUThe dictionaries we checked give it no style label and no Australian label, so it is everyday general English.
When pigs fly: what it is, and what it is not
- IS
- It will not happen; said with a laugh about the impossible.
- IS NOT
- About pigs flying through the sky like birds: it means that something will not happen.
Meaning: It will not happen; said with a laugh about the impossible.
How do people say it?
- In conversation:
Me, run a marathon? When pigs fly.
- At work:
A quiet week in December? That will happen when pigs fly.
Check yourself
What should I know?
The words say
Pigs flying through the sky like birds.
It really means
It will not happen.
What do dictionaries say?
- In Australia
- The dictionaries we checked give it no style label and no Australian label, so it is everyday general English.
- In the UK
- The dictionaries we checked give it no British label, so it is general English, not only from the UK.
- In the US
- The dictionaries we checked give it no American label, so it is general English, not only from the US.
What mistakes should I avoid?
- It is a laughing no for silly ideas. Do not use it to refuse a real request coldly.
- Pigs “fly” in this phrase. “When pigs swim” is not the idiom.
- Aim it at yourself or at fate. Aimed at a person's dream it can sound cruel.
The picture is a farmyard mutiny: heavy pink pigs rising over the barn, trotters paddling, farmers pointing up in disbelief.
It will not happen, cannot happen, and the speaker and the listener both know it — that shared knowing is the laugh. The phrase spends that laugh as a no.
“Me, run a marathon? When pigs fly” refuses with a grin instead of a frown, and the grin keeps friends. A bare “no” closes a door; the pigs close it with cake on the step.
The grin sets the limit. Aimed at yourself, at fate, at December ever being quiet, the phrase charms every room.
Aimed at another person's hope, it curdles fast: “when pigs fly” to a friend's bakery dream is not playful, it is a cold wind.
The test is whose dream pays for the laugh. If the answer is yours, fly the pigs freely. If it is theirs, ask a question instead, and let the bakery stand.
It roosts well with the small zoo of impossible skies. “Raining cats and dogs” sends pets down in earnest weather; “once in a blue moon” sets rarity one rung above the pigs.
Three skies, three measures: the downpour, the rare moon, the impossible pigs. Learn them as one shelf of weather-that-is-not-weather and each will steady the other two.
What else can I say?
- Pigs might fly British and dry; same laugh.
- Never in a million years Plain and strong.
- In your dreams Teasing; aim it at friends.
More idioms
- Once in a blue moon Very rarely; something that happens only now and then.
- Raining cats and dogs Raining very hard; a downpour.
More examples
- In a text:
Him on time? When pigs fly lol
Questions people ask
Is it rude?
Not when aimed at yourself or at silly ideas. Aimed at someone's real dream, the laugh turns cold, so ask a question instead.
What is “pigs might fly”?
The drier British cousin, said with one eyebrow up. It doubts aloud where the full phrase laughs.
Can I use it at work?
About shared silly hopes, such as a quiet December, yes. About a colleague's plan, choose plain honest words.
Sources and dates
- EasySay's own writing for the idioms, EasySay. Licence: original writing for EasySay. Checked .
Cite this page
EasySay. "When pigs fly". https://easysay.org/idioms/when-pigs-fly. Last updated 23 October 2026.
https://easysay.org/idioms/when-pigs-fly