When I saw or knew something, but currently I don't remember it, and after someone talks about it it revives my memory, what expression(s) may I use?

For some reason, probably heard someone saying but it's wrong, I got used to say: "sorry, it wasn't on top of my head".

I asked a native English speaker and he had trouble finding expressions for it.

I don't want something cold like "sorry, I couldn't remember". Something funnier, friendlier.

Is there an English expression for that? Any idea how I ended up with "on top of my head"? I actually like it, but I understand it is wrong.


  • 7
    I know what you're talking about, but I don't remember the expression off the top of my head.
    – Dan
    Commented Aug 5, 2022 at 22:21

4 Answers 4


The expression is:

off the top of your head (idiom)

from the knowledge you have in your memory:

  • "What's the capital of Mauritania?" "I don't know off the top of my head, but I could go and look it up."

(Cambridge Dictionary)

  • Right. It's off, not on, and the idea is that the idea was just lying in a stack at the top of one's mind. This is not suitable for detailed planning, but it's OK for estimates and immediate action. On the tip of my tongue, on the other hand, is more for remembering words and phrases than other kinds of facts. Same metaphor idea, except tongue for speech and head for ideas. Commented Aug 5, 2022 at 19:13
  • Thank you, so may I say "sorry, it wasn't off the top of my head"?
    – igorjrr
    Commented Aug 5, 2022 at 19:20
  • 7
    @igorjrr It would be more idiomatic to say "Sorry, I don't know off the top of my head", as in the above answer.
    – user888379
    Commented Aug 5, 2022 at 19:52
  • But at the time I say it, I remembered. So it seems it would be "Sorry, I didn't know off the top of my head". I still find it weird to say "I didn't know" because to me "it wasn't" but now it is.
    – igorjrr
    Commented Aug 5, 2022 at 20:18
  • True, but doesn’t fit OP circumstances.
    – Jim
    Commented Aug 5, 2022 at 23:35

On the tip of my tongue

If something that you want to say is on the tip of your tongue, you think you know it and that you will be able to remember it very soon:

  • Her name is on the tip of my tongue. (Cambridge)

Collins defines the same expression as meaning

that you are sure you know something, such as a word, an answer, or a name, but that you cannot remember it at the moment.

As an aside, there is also the word offhand, which used as an adverb means:

without looking for information and without thinking carefully; immediately:

  • I can't quote the exact statistics for you offhand, but they're there for you to see in the report. (Cambridge)

So in your situation it might be used to mean that you say something without trying too hard to remember exactly, without checking that the facts are exactly as you say.

  • 4
    This is the correct choice for knowledge we can or can't access immediately. Off the top of my head is not a memory issue, but a quick and dirty estimate without looking it up. Commented Aug 5, 2022 at 22:47
  • 1
    It's the source of a psychological term - the tip-of-tongue (TOT) phenomenon. Commented Aug 6, 2022 at 15:43

When you forgot to do something because it was lower priority, it’s because it wasn’t

top of mind


Foremost in one's thoughts; of greatest concern or priority.


Most likely you are conflating two different expressions on the tip of my tongue and off the top of my head and ending up with on the top of my head.

With on on the tip of my tongue you can say you know the answer you just need a bit of a nudge to get it out: “I know the answer, it’s just on the tip of my tongue, give me a few more details/seconds and I’ll have it”.

Not knowing something off the top of your head on the other hand is much less accessible. It requires active research to get the answer. It’s something that someone might know, but not something you know.

  • And getting something from the tip of your tongue to the top of your head requires some good juggling.
    – Barmar
    Commented Aug 7, 2022 at 20:17

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