In English, we often use idioms to describe people, situations, or emotions in a colorful and indirect way. One common type of idiom is used to describe someone who isn’t very smart in a funny, sarcastic, or sometimes rude way.
These expressions aren’t always polite, but they are very commonly heard in movies, conversations, and books. Learning these idioms helps you understand native English speakers better and adds a little humor to your vocabulary.
You’ve probably heard someone say, “He’s not the brightest bulb in the box,” or “She’s a few fries short of a Happy Meal.” These aren’t about light bulbs or food they’re creative ways of saying someone isn’t very smart.
In this guide, we’ll break down 35 popular idioms for stupid, explain what they mean, give clear example sentences, and show you other ways to say the same thing.
Contents
- 1 35 Common Idioms for Stupid (With Meaning & Examples)
- 1.1 1. Dumb as a rock
- 1.2 2. Not the sharpest tool in the shed
- 1.3 3. A few fries short of a Happy Meal
- 1.4 4. The lights are on but nobody’s home
- 1.5 5. Not the brightest bulb in the box
- 1.6 6. A few cards short of a full deck
- 1.7 7. Thick as a brick
- 1.8 8. Dumber than a bag of hammers
- 1.9 9. One sandwich short of a picnic
- 1.10 10. Elevator doesn’t go to the top floor
- 1.11 11. All foam, no beer
- 1.12 12. Not the quickest bunny in the forest
- 1.13 13. Doesn’t have both oars in the water
- 1.14 14. A few screws loose
- 1.15 15. A brick short of a load
- 1.16 16. A couple of sandwiches short of a picnic
- 1.17 17. Sharp as a marble
- 1.18 18. Born yesterday
- 1.19 19. Missing a few buttons on the remote
- 1.20 20. Not firing on all cylinders
- 1.21 21. Out to lunch
- 1.22 22. A few peas short of a casserole
- 1.23 23. Empty-headed
- 1.24 24. Doesn’t know which way is up
- 1.25 25. Head full of rocks
- 1.26 26. No sense of direction
- 1.27 27. Empty upstairs
- 1.28 28. Doesn’t have a clue
- 1.29 29. A couple of pickles short of a jar
- 1.30 30. In one ear and out the other
- 1.31 31. Half-baked
- 1.32 32. Not the full quid
- 1.33 33. Looney tunes
- 1.34 34. Not wrapped too tight
- 1.35 35. Lights are dim upstairs
- 2 Practice Makes Perfect: Fill in the Blank!
- 3 Conclusion
35 Common Idioms for Stupid (With Meaning & Examples)
Here we’re going to share 35 idioms for stupid, including their meanings, example sentences, and fun alternative phrases that express the same idea.
1. Dumb as a rock
Meaning: Extremely unintelligent
Example Sentence: Timmy is as dumb as a rock; he can’t even solve simple math problems.
Similar Sayings: Thick as a brick, Not the sharpest tool in the shed
2. Not the sharpest tool in the shed
Meaning: Lacking intelligence
Example Sentence: He means well, but he’s not the sharpest tool in the shed.
Similar Sayings: A few cards short of a full deck, Lights are on but nobody’s home
3. A few fries short of a Happy Meal
Meaning: Slightly crazy or not very smart
Example Sentence: That idea is just silly—you’re a few fries short of a Happy Meal.
Similar Sayings: Not playing with a full deck, Elevator doesn’t go to the top
4. The lights are on but nobody’s home
Meaning: They appear normal, but they’re not mentally present
Example Sentence: I tried explaining it to her, but the lights were on and nobody was home.
Similar Sayings: Empty upstairs, In la-la land
5. Not the brightest bulb in the box
Meaning: Not very clever or quick-thinking
Example Sentence: Jake’s not the brightest bulb in the box when it comes to technology.
Similar Sayings: Dim-witted, Half-baked
6. A few cards short of a full deck
Meaning: Lacking common sense or intelligence
Example Sentence: He acts a bit strange—like he’s a few cards short of a full deck.
Similar Sayings: Off his rocker, Not quite right
7. Thick as a brick
Meaning: Very stupid or dense
Example Sentence: She’s as thick as a brick when it comes to reading social cues.
Similar Sayings: Clueless, Blockhead
8. Dumber than a bag of hammers
Meaning: Completely unintelligent
Example Sentence: That guy is dumber than a bag of hammers!
Similar Sayings: Dull as dishwater, Brain-dead
9. One sandwich short of a picnic
Meaning: A little crazy or not very clever
Example Sentence: I’m not sure what he was thinking—he’s one sandwich short of a picnic.
Similar Sayings: Nutty, Loopy
10. Elevator doesn’t go to the top floor
Meaning: Missing intelligence or common sense
Example Sentence: He’s nice, but his elevator doesn’t go to the top floor.
Similar Sayings: Missing a screw, Not all there
11. All foam, no beer
Meaning: Looks good on the outside, not much substance inside
Example Sentence: He talks a big game, but he’s all foam and no beer.
Similar Sayings: Empty suit, No depth
12. Not the quickest bunny in the forest
Meaning: Not very smart
Example Sentence: Bless her, she’s not the quickest bunny in the forest.
Similar Sayings: Slow on the uptake, Not too sharp
13. Doesn’t have both oars in the water
Meaning: Not thinking clearly
Example Sentence: After that strange idea, I wonder if he has both oars in the water.
Similar Sayings: Not all there, Off-balance
14. A few screws loose
Meaning: Slightly crazy or not quite sane
Example Sentence: That plan sounds like it came from someone with a few screws loose.
Similar Sayings: Nuts, Not wrapped too tight
15. A brick short of a load
Meaning: Missing intelligence
Example Sentence: That guy’s a brick short of a load if he thinks that’ll work.
Similar Sayings: Dim, Not the full ticket
16. A couple of sandwiches short of a picnic
Meaning: Not very smart
Example Sentence: She’s sweet, but clearly a couple of sandwiches short of a picnic.
Similar Sayings: Not all there, Scatterbrained
17. Sharp as a marble
Meaning: Extremely dull or unintelligent
Example Sentence: He’s about as sharp as a marble when it comes to solving problems.
Similar Sayings: Brain-dead, Dull
18. Born yesterday
Meaning: Very naïve or foolish
Example Sentence: Do I look like I was born yesterday?
Similar Sayings: Gullible, Green
Meaning: Not fully functional mentally
Example Sentence: He acts like he’s missing a few buttons on the remote.
Similar Sayings: Not wired right, Something’s off
20. Not firing on all cylinders
Meaning: Not thinking clearly
Example Sentence: He was tired and not firing on all cylinders during the meeting.
Similar Sayings: Foggy, Out of it
21. Out to lunch
Meaning: Mentally absent
Example Sentence: I asked her a question, but she was totally out to lunch.
Similar Sayings: Zoned out, Spaced
22. A few peas short of a casserole
Meaning: Mentally lacking
Example Sentence: That guy is a few peas short of a casserole.
Similar Sayings: One can short of a six-pack, Loopy
23. Empty-headed
Meaning: Not intelligent or thoughtful
Example Sentence: She’s beautiful but completely empty-headed.
Similar Sayings: Airhead, Bubblehead
24. Doesn’t know which way is up
Meaning: Very confused or clueless
Example Sentence: He doesn’t even know which way is up right now.
Similar Sayings: Lost, Disoriented
25. Head full of rocks
Meaning: Not intelligent
Example Sentence: He must have a head full of rocks to believe that story.
Similar Sayings: Thick-skulled, Dense
26. No sense of direction
Meaning: Can’t think clearly or make good decisions
Example Sentence: She has no sense of direction in life or logic.
Similar Sayings: Clueless, Aimless
27. Empty upstairs
Meaning: Mentally vacant
Example Sentence: He looks sharp, but he’s totally empty upstairs.
Similar Sayings: Vacant, Airhead
28. Doesn’t have a clue
Meaning: Completely uninformed
Example Sentence: He doesn’t have a clue how to fix that.
Similar Sayings: Clueless, In the dark
29. A couple of pickles short of a jar
Meaning: Not all there mentally
Example Sentence: That idea makes no sense—he’s a couple of pickles short of a jar.
Similar Sayings: Not right in the head, Nutty
30. In one ear and out the other
Meaning: Doesn’t retain information
Example Sentence: I told him three times—it just goes in one ear and out the other.
Similar Sayings: Forgetful, Doesn’t listen
31. Half-baked
Meaning: Not well thought out
Example Sentence: That’s a half-baked plan if I’ve ever heard one.
Similar Sayings: Silly, Flawed
32. Not the full quid
Meaning: Lacking intelligence (British slang)
Example Sentence: He’s charming but not the full quid.
Similar Sayings: Off, Not right
33. Looney tunes
Meaning: Slightly crazy or silly
Example Sentence: That guy is totally looney tunes.
Similar Sayings: Wacky, Bonkers
34. Not wrapped too tight
Meaning: Slightly crazy or mentally off
Example Sentence: He’s not wrapped too tight if he thinks that’ll work.
Similar Sayings: Cuckoo, Off the rails
35. Lights are dim upstairs
Meaning: Lacks intelligence
Example Sentence: Poor kid, the lights are dim upstairs.
Similar Sayings: Not all there, Not too bright
Practice Makes Perfect: Fill in the Blank!
Try to complete the sentences using the idioms you just learned:
-
Sarah tried to solve the math problem, but she’s _______________.
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I like him, but he’s not the _______________ in the shed.
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That idea makes no sense—he must be _______________.
-
She looks great, but honestly, she’s _______________.
-
He couldn’t even open the app—he’s as _______________ as a rock.
-
Sometimes I wonder if she has _______________ in the water.
-
Don’t trust him with anything important—he’s _______________.
-
He was so lost in class today, totally _______________.
-
He’s a great guy, but not exactly _______________ in the box.
-
I gave him clear directions, but it went _______________.
Answers
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dumb as a rock
-
sharpest tool
-
a few cards short of a full deck
-
empty-headed
-
dumb
-
both oars
-
not the full quid
-
out to lunch
-
the brightest bulb
-
in one ear and out the other
Conclusion
So there you have it colorful idioms for stupid that English speakers love to use.
These expressions might sound funny, but they carry meaning in everyday conversation.
Next time someone says, “He’s not firing on all cylinders,” or “She’s a few fries short of a Happy Meal,” you’ll know exactly what they mean and maybe even smile a little.