Is there a subtle or significant difference in meaning between the following?

  1. fill something in

  2. fill something out

In my humble opinion, the two expressions are interchangeable and both mean to complete something, usually it's a form or an official document by filling in the blank spaces or filling it out i.e. become full.

However, is it true in some American English dialects, fill in means to supply information whilst fill something out means to complete something in its entirety?

This piece of information was imparted to me by a very competent American English speaker.

I am referring to an aspectual difference when out is used in conjunction with the verb.

I disagreed, based on instinct (common sense?), I sustain that there is no difference in meaning between the two. Oxford Living Dictionaries doesn't mention this subtle difference in meaning but I'm not an American English native speaker, maybe the user is onto something?

  • Possibly of related interest: “Fill out a form” or “fill in a form” and Does “filling out” equal to “filling in”?
    – choster
    Commented Feb 1, 2018 at 22:57
  • By “complete something in its entirety” they mean anything, not only in reference to documents?
    – user 66974
    Commented Feb 1, 2018 at 22:57
  • As a native AmE speaker, I agree with the AmE speaker who said they're different. See especially the second of choster's links.
    – Kevin
    Commented Feb 1, 2018 at 23:01
  • 4
    They are ambiguous. But generally, in the US, "fill out" means to "complete" the form -- supply all applicable information. "Fill in" means to put specific data in a specific place. Eg, "fill in your Social Security" number. But, as I said, they are ambiguous, and context must be considered.
    – Hot Licks
    Commented Feb 1, 2018 at 23:39
  • 1
    I agree with your friend. "Fill in" and "fill out" are not quite interchangeable. You can fill in a box on a form, or you can fill in an entire form. You cannot "fill out" a single box on a form.
    – user85627
    Commented Feb 2, 2018 at 9:03

5 Answers 5


The distinction between fill out and fill in is rather ambiguous.

Generally speaking, in the US, "fill out" means to "complete" the form -- supply all applicable information. "Fill in" means to put specific data in a specific place. Eg, "fill in your Social Security" number.

But, as I said, this distinction is not especially strong, and the context should be taken into account to hopefully either confirm or contradict this general assumption.

  • 4
    This is an unsupported POB answer. Can you provide evidence?
    – user 66974
    Commented Feb 2, 2018 at 14:56
  • 2
    @Mari-LouA I beg to differ, in case of what is being "used", I heard "fill in your reports" many often here in southern California. So it does not only mean one specific data as this answer states.
    – ib11
    Commented Feb 2, 2018 at 15:57
  • 2
    @user159691 In your answer, the blogger, who's not a lexicographer or a linguist, is just someone like me or yourself, someone who happens to be interested in the English language. He is not even an American English speaker, he's Irish ( I checked ). Hot Licks is American, he's a competent speaker, so I trust his interpretation, and I appreciated his objectivity.
    – Mari-Lou A
    Commented Feb 2, 2018 at 17:42
  • 4
    @Mari-LouA - you are obviously free to appreciate whatever you like, but given that ELU covers a wider audience, an unresearched and POB answer without any evidence in not the best we can offer.
    – user 66974
    Commented Feb 2, 2018 at 17:57
  • 3
    FWIW, this fits my experience as a native AmE speaker, primarily in the Midwest and Los Angeles. I appreciate the hedging in the answer—it is possible to say fill in the form even if it's unusual (and might have slightly different implications). On the other hand, I would say it is unusual to the point of "wrong" to say fill out the blanks (on the form).
    – 1006a
    Commented Feb 3, 2018 at 2:16

Yes, they both definitely mean that but one is American, the other one is British, however both are in use in AmE per my experience, as to the different aspect:

Fill something out per ODO:

North American

1 Add information to complete an official form or document.
‘he filled out the requisite forms’

Fill something in per ODO:

1.2 British Add information to complete something, typically a form or other official document.

‘he filled in all the forms’

And I agree with the AmE speaker who said they seem different in aspect. And I believe that difference in aspect comes from the adverbs in and out that are part of the two phrasal verbs.

fill + in

From Merriam-Websters in:

1 c : to or at an appropriate place

fill + out

From Merriam-Websters out:

3 b : to completion or satisfaction

3 c : to the full or a great extent or degree

Please also note comment below from @tchrist, where he points out the very good point that both AmE and BrE have their own idiomatic uses. In my answer I strictly intended to point out the difference between AmE and BrE in meaning "to complete a form", and the difference between the adverbs.

  • 4
    The (paywalled) OED does not make any sort of US–UK distinction between the two. Note that each still has idiomatic uses that resist casual substitution of one for the other. A person who was previously super-skinny but has since put on healthy weight can ᴏɴʟʏ be said to have filled out and ɴᴏᴛ to have filled in, whereas potholes in the street that get fixed can ᴏɴʟʏ be said to have been filled in and ɴᴏᴛ to have been filled out.
    – tchrist
    Commented Feb 2, 2018 at 14:06
  • It's not clear to me if this answer is attempting to say that AmE speakers are unlikely to say "fill in". My experience is that AmE speakers use both "fill in" and "fill out" and the connotations are generally exactly as the asker describes. Americans are very likely to "fill in the blanks" in order to "fill out the entire form". Students in school are often presented with "fill-in-the-blank tests". Commented Feb 2, 2018 at 16:52
  • @ToddWilcox No, it does not, it merely quotes the dictionaries, and points out the difference between the adverbs, as a possible reason for the seemingly existing difference. I did hear a lot "fill in" for "fill out" in Los Angeles.
    – ib11
    Commented Feb 2, 2018 at 17:46
  • 1
    I think that distinction between AmEng and BrEng usage is less marked than it was in the past. Cambridge Dictionaries (British) does not assign any dialect to one variant dictionary.cambridge.org/dictionary/english/…
    – Mari-Lou A
    Commented Feb 2, 2018 at 18:12
  • 2
    @tchrist Fry and Laurie, 1987: “Would you like to fill out a form?” “Fill out a form? Fill out a form? You mean fill in a form! Has everyone suddenly turned American?” Commented Feb 3, 2018 at 8:32

In British English, we would understand both "fill it out" and "fill it in" to mean the same thing with regard to e.g. a form – though I believe "fill it in" would be more commonly used.

I think "fill this out" would sound more awkward to British ears, but "fill that out" less so, because the implied distance in 'that' matches the tone of 'out'.

However, if it's with regard to a person, only "fill in" is used – e.g. "Can you fill me in on the meeting I missed?", or "Please fill Tom in on the details". We would not say "Please fill me out".

  • 1
    as a native BrE speaker I have heard'Fill this out' used when handing a form to somebody, whereas 'fill that out' used both when handing a form or when pointing to where the form can be located. - neither method sounds awkward they would just be used in slightly different contexts
    – EdHunter
    Commented Feb 2, 2018 at 15:45

These are often used interchangeably, but they have slightly different connotations. The difference is:

"Fill this in" is definitely singular, while

"Fill this out" typically refers to a plurality

This is obvious if you consider the word "in". In order to "fill something in", there must be some thing (singular) to put a response inside.

As an example, "in" would be preferred for this strictly singular case:

"Fill in the box" (There's a single box)

This is difficult when referring to a form, because a form is a collection of boxes to be filled out. Thus it can be:

"Fill in a form" (referring to the singular form)


"Fill out a form" (referring to the collection of elements that make up the form)

As a final example:

"Fill out these forms"

would be less awkward than

"Fill in these forms"

However, they're both technically correct, since the collection of forms could be interpreted as a single item.


The following extract may help understand the usage of fill in vs fill out also from the BrE perspective vs the AmE one:

Of the two, fill in seems more logical. If you’ve got a form, it has blank spaces which you have to fill by putting information in those spaces. Fill on its own wouldn’t work, not in reference to the form as a whole. You fill the spaces, sure, but filling a form would feel like you were covering every last millimetre of the form with ink. And that’s probably not what you’re supposed to do.

So what about fill out then? First of all, it seems like it’s used more often in American English than British English. Searching the Corpus of Contemporary American EnglishCorpus of Contemporary American English provides more results for fill out a form than fill in a form. This may be a result of the influence of German-speaking immigrants on American English, as the German phrase ausfüllen can be directly translated to fill out. I’ve tried checking the British National Corpus, but it’s not working as of time of writing. Anecdotally though, it seems fill in is more common in British English. Here in Ireland we tend to use both, as we’re exposed to both British and American English quite often.

Thinking now actually, even though fill in might seem more logical, fill out also seems kind of logical. It makes sense in terms of filling out a whole form, as the out conveys a sense of expansiveness, probably related to the concept of outside that goes along with it.

For a lot of people, I think it makes sense to say fill out a form, but perhaps fill in a specific section of a form. That’s probably why, when we want someone to give us information, we tell them to fill us in. We want them to put this specific information in our mind, like when we fill in a particular section of a form. Fill us out just wouldn’t make sense in that context.


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