In a meeting I've asked someone a question and in response she said:

I'll let you know when I find out

From her tone, I know that she didn't mean to be rude or anything, so I just want to know what a native speaker will get from it. Will you consider it a normal sentence, or rude or even funny?

Clearly, I am not a native English speaker, but I've expected to hear something like:

I will inform you

Or something like that.

  • It means "I don't know, but when I find out I'll inform you."
    – Robusto
    Mar 19, 2017 at 0:56
  • It sounds fine in writing. Tone, facial expression and body language could counter that, of course.
    – WRX
    Mar 19, 2017 at 0:56
  • 2
    I will inform you sounds quite formal and unfriendly
    – Chris M
    Mar 19, 2017 at 1:14
  • "I'll let you know when I find out" is pretty much a set phrase that is intentionally vague. If she doesn't find out you will never know it. It would be the same result as if she finds out but doesn't tell you.
    – user3169
    Mar 19, 2017 at 1:14
  • It is not the words that are rude. It's the tone which is or isn't rude.
    – Lambie
    Apr 21, 2021 at 14:21

5 Answers 5


It's not rude at all to tell someone

I'll let you know

It either can mean you don't know or you haven't made up your mind.
Less ambiguous is

I'll let you know when I find out.

since it means you don't actually know at the time you were asked. A short hand form might be

When I know, you'll know.

Which can mean when you find out you will tell them, it can also mean you will all be told at the same time.

What is rude is if you told someone you'd let them know and then never say anything.


To say I will inform you is very formal and does not give the impression that they are being friendly. It is too formal and a more friendly way of saying it is exactly as you heard it - 'I'll let you know'. Basically therefore, this is what you should expect to hear.


In addition to the previous answers I wish to add that both "I'll let you know" and "I'll inform you" are not rude, but depending on the context in speech and the situation either of them can be rude.

  • I'll inform you - is, as I think, more formal and more professional.
  • I'll let you know - is more common in everyday English and is less strict than the previous phrase.

To see the bigger difference, "I'll inform" is closer to "I will tell you personally", while "I'll let you know" can either mean "I will tell you personally" or "someone or something else will inform you"—in either case in result you will be informed.


To me, I am 'informed' of very important information. One tends to hear this from doctors, policeman, judges, and others giving legal information. You can make an informed decision about something important when you have all the facts, get a second opinion, do research. You are informed when your real estate bid is accepted.


To me it is not rude they both mean the same thing. It depends on the environment and the person your telling this to wether it should be more formal sounding like "I let you know" if formalities is required then it would be rude I assume.

  • 2
    This adds nothing to the accepted answer.
    – Chenmunka
    Apr 23, 2023 at 7:43

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