Title case: the rules, and where the style guides disagree

There is no single correct way to capitalise a title. The major style guides draw the line in different places, and Chicago moved its own line in 2024.

Published 3 November 2026

There is no correct way to capitalise a title. There are several competing conventions, each internally consistent, each used by serious publishers, and they produce different results for the same words. A title that is right in a newspaper is wrong in a journal.

Worse, the conventions move. The Chicago Manual of Style changed its preposition rule in 2024, so a title that was correct Chicago style in 2023 may not be correct Chicago style now.

What everyone agrees on

The large majority of any title is uncontroversial. Every style capitalises:

The first word, always, whatever it is. Even “the” or “a”.
The last word, always, for the same reason.
Nouns, pronouns, verbs, adjectives and adverbs — the words carrying the meaning. This includes short ones: Is, Be and It are capitalised because they are verbs and pronouns, not because of their length.
The word after a colon, which starts a subtitle.

And every style lowercases the articles — a, an, the — in the middle of a title, along with the coordinating conjunctions and, but, or, nor, for, yet and so.

So the entire disagreement is about one part of speech: prepositions.

Where the styles split

Two philosophies. AP and APA draw the line by length — a long word looks important, so capitalise it. Chicago historically drew it by part of speech — a preposition is a function word regardless of how long it is, so lowercase it.

In 2024 Chicago moved most of the way towards the length-based camp.

Style	Prepositions lowercase at	“with”	“about”	Example
AP	3 letters or fewer	With	About	Gone With the Wind
Chicago, 18th ed. (2024)	4 letters or fewer	with	About	Gone with the Wind
Chicago, 17th ed. and earlier	any length	with	about	Much Ado about Nothing
APA	3 letters or fewer	With	About	Gone With the Wind

The 2024 Chicago change

From its 12th edition in 1969 until its 17th, Chicago said to lowercase prepositions regardless of length. That gave Much Ado about Nothing, which strikes many people as wrong on sight, and was a reliable way to tell Chicago-styled text from everything else.

The 18th edition, published in 2024, capitalises prepositions of five letters or more. Chicago’s own announcement gives the two examples that define the new boundary: A Room with a View keeps its lowercase with at four letters, while Much Ado About Nothing now takes a capital About at five.

The same edition renamed the style itself: what Chicago used to call “headline style” is now simply “title case”.

One practical consequence: AP and Chicago now differ only on prepositions of exactly four letters — with, from, into, over, like, near, onto, past, than, down, upon and a handful more. Everything shorter is lowercase in both; everything longer is capitalised in both.

MLA, honestly

We could not confirm MLA's current rule

Secondary guides contradict each other on MLA: some say it capitalises any word of four letters or more, others that it lowercases articles, prepositions and coordinating conjunctions regardless of length. The page MLA used to publish on this is no longer at its old address, and we are not going to settle the question by picking the version that appears most often in blog posts. If you are writing to MLA, check the current MLA Handbook.

Why no converter can be completely right

A title case tool has to decide, word by word, whether something is a preposition. That is not a property of the word — it depends on how the word is being used, and software that does not understand the sentence cannot know.

The same word, two parts of speech. In Walk up the Hill, “up” is a preposition and Chicago lowercases it. In Look Up the Answer, the same three letters form part of the verb and should be capitalised. Chicago is explicit that prepositions used adverbially or adjectivally are capitalised — The On Button — which is correct and impossible to automate reliably.

Acronyms. A converter that lowercases everything and then capitalises initials turns NASA into Nasa and HTML into Html. The protection is to leave words that are already fully capitalised alone, which works until the whole input is capitals — at which point every word looks like an acronym and the text that most needs fixing would come back untouched.

Deliberate lowercase. iPhone, eBay and names styled in lowercase by their owners are all damaged by naive capitalisation, and no rule distinguishes them from a typo.

Proper nouns in reverse. Sentence case has the mirror-image problem: lowercasing everything but the first word cannot tell Bill the person from bill the invoice.

None of this makes a converter useless. It makes it a first pass that saves the bulk of the work, with the proper nouns and the genuinely ambiguous words still needing a human read. Any tool claiming otherwise is overselling.

How Celveri’s converter behaves

The case converter offers Chicago and AP, and Chicago follows the 18th edition rule — five letters or more take a capital. It always capitalises the first and last word, and the word opening a subtitle after a colon. Both halves of a hyphenated compound are capitalised, giving A Well-Known Problem. Acronyms are left alone by default, with the all-capitals exception described above, because text typed with caps lock on is exactly what people arrive wanting to fix.

It also offers “capitalise each word”, which is not title case and is sometimes what you actually want — for labels and menu items where the small words looking lowercase reads as a mistake.

What to do in practice

If a style is mandated, follow it. A journal, publisher or employer that specifies AP or Chicago has settled the question.
If nothing is mandated, pick one and be consistent. Consistency across a site or a document is far more visible to a reader than which convention you chose.
Consider sentence case. Capitalise the first word and the proper nouns, and stop. It sidesteps every disagreement on this page, never has to be re-checked when a style guide is revised, and is why a good many product and documentation teams have standardised on it.
Read the result. Whatever produced it, look at it once. Automated capitalisation fails in small, specific, obvious-to-a-human ways.

Sources

Style rules change between editions, so these are linked rather than summarised and trusted.

Chicago: announcing the 18th edition — The publisher's own blog, where the preposition change is stated directly.
Chicago Manual of Style Q&A: titles — Chicago's answers on capitalising titles, including the history of the old rule.
APA Style: title case — APA's own guidance on which words take capitals.
AP Stylebook — The authority for AP, but subscription-only — there is no free official page to cite.

If you are counting characters in a headline as well as capitalising it — because a page title is cut off in search results at around 60 — counting is its own can of worms.

Tools that help with this

Text Case Converter
Switch between sentence case, title case, upper, lower and code styles.
Word Counter
Count the words in a passage as you type or paste it.

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