As far as I observed people would use when instead, but still, I wonder if the sentences below are grammatically correct.

  1. How many days later will you come (back)?
  2. After how many days will you be here (again)?
  3. How many days from now will you be there?
  4. How many days later from now will you go there?
  5. How many days later from then will you go there? (future of future)
  6. After how many days from now will you go there?
  7. After how many days from then will you go there? (future of future)

So, which of the sentences above are grammatically correct? Also what would be the correct structure for the incorrect (or poorly worded) ones? Thank you.

1 Answer 1


As you say, "people would use when".
Although most of your sentences are grammatically correct, the wording is not colloquial. So there is no "correct structure for the incorrect ones". They need to be rewritten.

Rather than how many days, we (in the UK) might ask:
When will you be back?
When are you coming back?
How long will you be there?
How long are you staying?

We might ask:
How many days are you going for?
How many days will it take (you) to get there?
but asking "when" or "how long" allows the other person to answer in days of the week or dates: "(Until) Tuesday" or "(Until) May the 30th".

Also, "when do you go", "when will you go" and "when are you going" can all be used to speak about the future.

I'm afraid there is no easy answer to your question!

  • Thank you for your answer. Do you have an explanation why sentence 3 is correct without 'later' as in sentence 4? Is there a difference in meaning between sentences 3 and 4 (assuming both have the same verb, either 'be' or 'go')?
    – Xfce4
    Jun 22, 2021 at 3:20
  • Do you understand that a grammatically correct sentence can be utterly meaningless? The meaning of sentence 3 can only be guessed at. It should probably be "In how many days' time will you get there". "How many days will you be there" means" How long will you stay there", but "from now" in the middle makes its meaning only guessable. Sentence 4 is meaningless. It needs either "later" or "from now". Each would mean something different. Jun 22, 2021 at 3:53
  • If sentence 3 was 'How many days from now will you leave for London?' is it gramatically correct and meaningful? Also, do you mean that I should not use 'later' and 'from now' at the same time in sentence 4? Is it counted as a mistake or just verbose? The same arguments apply to sentence 5, too?
    – Xfce4
    Jun 23, 2021 at 5:51
  • No. Not quite. It would be understood, but it means the person will 'leave days'. "In how many days' time do you leave for London" would be g.c. and m. Please learn the formula: in three days' time. What I mean about sentence 4 is what I said about it. Read my comment. Why persist with the words "how many days" when I've told you there are many better ways to say what you are trying to say? Jun 23, 2021 at 12:07
  • It may help if you go [here[(learnenglish.britishcouncil.org/english-grammar-reference/…) and learn how to talk about the future. "When are you going to London", "When do you go to London" etc. Jun 23, 2021 at 12:09

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