If I hear someone ring the doorbell and suspect it is the postman, should I say "That would be the postman" or "That will be the postman"? If both are okay, what is the difference?

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    In contexts like this, most native speakers refer to what we think the current situation IS by saying what WILL be found to be the case when we discover the actual truth. But it's also perfectly idiomatic for at least some speakers to use would - as if to say, that's what we would find to be the case if we looked into it (which we might not actually do anyway, because the result is a foregone conclusion). Sometimes we need Past Tense: "Someone rang the doorbell while I was brushing my teeth", "That would be the postman" (perhaps more often, would've been). Mar 26, 2021 at 13:02
  • Are you saying the would-version involves a conditional?
    – Apollyon
    Mar 26, 2021 at 13:21
  • Could the "would" be an epistemic modal, having nothing to do with conditionals?
    – Apollyon
    Mar 26, 2021 at 14:12
  • I think that just nets down to how you describe the choice of verb tense/mood. As I often say, I don't care much about these labels (native Anglophone rarely know what they mean anyway, so obviously such labels aren't necessary to learn English. From my perspective (having just looked up epistemic modality on Wikipedia), I can't really see much difference between That would be the postman and That must / might / may be the postman, but neither will not would appear at all on that Wikipedia page... Mar 26, 2021 at 15:43
  • ...I mean I don't see much difference in terms of them all conveying something about speaker's belief (re something that might or must be true). Obviously there convey different strengths of belief. Whatever - I see a "conditional" element on the grounds that we say THAT WOULD BE X to mean IF we were to check it out, which we're probably not going to do, THAT'S WHAT WE WOULD FIND (ditto with WILL instead of WOULD). But if that perspective doesn't help you understand how the usage comes to exist, just forget I said it. Mar 26, 2021 at 15:50

2 Answers 2


"Will" implies certainty, while "would" implies a possibility.

"That will be the postman" tells the listener that you're certain the postman is there. Combined with the future tense, this makes little sense, as there is no guarantee that you can predict the future.

"That would be the postman" tells the listener that you're believing the postman is there. Combined with the future tense, this makes perfect sense, as there is no guarantee that you can predict the future.

In commonly spoken English, this distinction is often lost; but, if you make the distinction you are seen as a better user of English.

Related to this is the difference between "Can you get the door?" and "Would you get the door?" The first one asks about physical ability, while the second one asks if someone is willing to perform the action. There are always people who are physically able to get a door that won't, so better English would have you asking "Would" instead of "Can" when asking for a favor to be performed.


That'll be the postman.

Is a nice natural thing to say. In practice you don't need to say anything. It's not uncommon for people to naturally talk to themselves like this, but it's not something that you need to do. "That'd be the postman" would be fine too. It's not something that you would normally use in an un-contracted form. Using "would" might indicate greater certainty than "will".

I don't want to overanalyse this. But if you do then see Sematics of epistemic modals

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    I disagree, we often say in English, in hearing a doorbell ring or someone knocking on a door: "Ah, that would be John." And it would be very often non-contracted.
    – Lambie
    Mar 26, 2021 at 17:16
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    "We" might, but I wouldn't (!)
    – James K
    Mar 26, 2021 at 17:24
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    Oh, right, so you would say: That'd be John?
    – Lambie
    Mar 26, 2021 at 17:29
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    +1 in particular for not wanting to "overanalyse" the usage. Imho, far too many learners are being taught (indifferently observed / recognised) tendencies in relation to epistemic modals as if they were rules. Mar 26, 2021 at 17:49

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