All Their Or All Of Their | Grammar Choice That Fits

Writers bump into the choice between “all their” and “all of their” all the time. Both forms appear in books, news articles, and everyday speech, so it is easy to wonder which one is right and when it matters.

This article walks through clear patterns, real sentences, and simple checks you can use. The goal is to help you pick a form that fits your sentence, your tone, and the expectations of careful English readers.

All Their Or All Of Their In A Nutshell

In modern English, both “all their” and “all of their” are grammatically correct before a noun. The word “of” is usually optional when “all” comes before a determiner such as a possessive like “their.” Grammar references treat the versions as a pair, with small differences in style and rhythm rather than strict rules.

Context	Preferred Choice	Sample Sentence
Short, direct statement	all their	The students finished all their work on time.
Slightly formal or careful tone	all of their	The students finished all of their work on time.
Fast, conversational speech	all their	The players sold all their old gear.
Rhetorical emphasis on extent	all of their	The storm ruined all of their stored grain.
Short headline or title	all their	Family Donates All Their Savings To Charity
After long noun phrase	either form	The committee members and volunteers gave all their time.
Before pronoun “them” (for contrast)	all of them	She thanked all of them for coming.
Very formal legal or academic style	often all of their	The parties shall disclose all of their relevant records.

The first column shows typical situations. The middle column shows the form that feels more natural in that context, and the third column gives a model sentence. You can already see that the noun after “their” matters more than the tiny word “of.”

How All Works Before Possessives

The word “all” can act as a determiner before a noun phrase. When that noun phrase starts with a possessive determiner such as “my,” “your,” “our,” or “their,” English allows “all” either with or without “of.” A resource like Cambridge Grammar on “of” with “all” describes “of” as optional here, not required.

That is why you meet pairs such as “all their books” and “all of their books,” “all our plans” and “all of our plans,” or “all my life” and “all of my life.” In each case, “all” refers to the complete set, while the possessive determiner marks who owns or experiences that set.

Role Of “Of” In These Phrases

When “all” comes before a pronoun alone—“all them,” “all us,” “all her”—standard grammar usually calls for “of”: “all of them,” “all of us,” “all of her.” This pattern helps explain why many learners assume “of” is required everywhere, yet it is only required in a narrow set of structures.

The pair “all their + noun” and “all of their + noun” behaves differently. Here, “their” is already a determiner before the noun, so “of” becomes optional. That is why both “all their time” and “all of their time” work, while “all them time” does not.

Choosing All Their Versus All Of Their In Writing

Once you know both versions are acceptable, the real question becomes style. Writers usually pick the form that sounds natural in a sentence and fits the kind of text they are working on.

When Concise Language Helps

“All their” uses one fewer word, so it often sounds slimmer and quicker. In news reports, blog posts, and informal emails, that lighter feel can suit the tone. “The team lost all their matches” keeps the line quick and punchy.

Shorter phrases also stack more easily when you have several modifiers. “They shared all their new lesson ideas” reads cleanly. “They shared all of their new lesson ideas” still works, yet the extra syllable in “of” stretches the rhythm a little.

When Extra Emphasis Feels Right

Writers sometimes pick “all of their” when they want extra weight on the total amount or on the owners. In “The storm destroyed all of their crops,” the phrase draws attention to the loss, not just to the crops themselves. The tiny word adds a pause that slows the line and gives it more punch.

The same effect appears with emotional topics: “She gave all of their savings to charity,” “He spent all of their free weekends on the project.” In each case, the phrase invites the reader to pause on how much was given up.

Formal And Academic Tone

In academic and legal writing, many editors allow both forms as long as the writer stays consistent. Style blogs, such as Proofed’s guide to “all” versus “all of”, note that “all of” often sounds slightly more formal than “all” alone, though both are grammatically sound.

If you write essays, reports, or policy documents, you can pick the version that your instructor, institution, or house style prefers. Many writers choose “all their” in general explanation and “all of their” when quoting or paraphrasing source material with that form.

Common Patterns With All Their And All Of Their

Seeing common collocations can make the choice easier. Certain nouns appear so often with these phrases that your ear starts to recognise them as standard patterns.

Time Expressions

English uses both “all their life” and “all of their life,” with plural “lives” when you talk about more than one person. A corpus search shows both “all their lives” and “all of their lives” in published writing. Many speakers feel “all their lives” sounds slightly lighter, while “all of their lives” feels a touch more solemn.

Belongings And Abstract Nouns

With concrete nouns such as “belongings,” “things,” “books,” and “clothes,” you again find pairs: “all their belongings” and “all of their belongings.” Dictionaries and usage databases show both forms in natural examples, with no difference in basic meaning.

The same pattern holds for abstract nouns. Writers switch between “all their effort” and “all of their effort,” “all their attention” and “all of their attention,” depending on tone and rhythm. Learners can safely treat both as acceptable and focus more on overall sentence clarity.

Idiomatic Fixed Phrases

Some expressions lean strongly toward one form, often for historical reasons. For instance, “all their fault” appears more often than “all of their fault,” while “all of their number” feels more formal and old-fashioned. Reading widely helps you absorb these preferences over time.

Next Word After “All”	Correct Option(s)	Example
their + noun	all their / all of their	The children packed all their toys.
them (pronoun only)	all of them	Invite all of them to the event.
the + noun	all the / all of the	She checked all the answers twice.
uncountable noun, no determiner	all (no “of”)	All water in the tank froze overnight.
possessive pronoun (theirs)	all theirs	The victory was all theirs in the end.
proper noun for a class	all (no “of”)	All London buses stopped during the strike.
relative pronoun “that”	all that	All that money disappeared in days.

This table reminds you that the “all their / all of their” choice sits in a wider family of “all” phrases. Once you know how “all” behaves with pronouns, determiners, and bare nouns, the puzzle feels much smaller.

Common Mistakes To Avoid

Thinking One Form Is Wrong

A frequent learner error is to treat “all of their” as correct and “all their” as broken English, or the other way round. Standard references and real-world examples show that both forms sit inside normal usage. The difference lies in tone, not in basic grammar.

If a teacher or editor has a clear preference, follow it for that course or publication. Outside that setting, you can relax and choose the version that feels natural in context.

Copying Every Example Without Checking Register

Because both phrases appear in many settings, it helps to pay attention to register. A casual text message, a newspaper headline, and an academic article do not always share the same habits. If your model sentence comes from a formal report, “all of their” may match that style. If it comes from song lyrics or dialogue, “all their” may sound closer to everyday speech.

When in doubt, check respected dictionaries or grammar sites for patterns and sample sentences around the noun you plan to use. Over time, your ear will grow more sensitive to the small style difference between the two versions.

Mixing Up Their And Theirs

Another common issue has nothing to do with “of” at all. Learners sometimes confuse “their” (a determiner) with “theirs” (a possessive pronoun). You write “all their books” but “the books are all theirs.” The first case needs a noun after “their,” while the second does not.

Keeping that contrast clear helps you avoid confusing forms such as “all of theirs books,” which combines both words in one spot. In that structure, the sentence should read either “all of their books” or “the books are all theirs.”

Simple Checklist For Learners

Three Quick Questions

When you want to write all their or all of their, you can run a short mental check. Ask yourself three questions before you settle on one version.

• What word comes right after “their”?
• How formal do I want this sentence to sound?
• Does the line sound smooth when I read it aloud?

If the word after “their” is a noun, you know both forms work. If the sentence sits in a relaxed email, text, or chat, “all their” will often feel natural. If you write a speech or a line where you want the listener to feel the weight of the phrase, “all of their” can help.

Practice Ideas

One simple practice task is to collect pairs from your reading. Each time you see “all their” or “all of their” in an article, story, or textbook, write the sentence down, then rewrite it with the other form. Say both versions out loud and listen for the change in rhythm.

You can also draft your own mini paragraphs about real topics in your life—classes, family, hobbies—and push yourself to use both patterns. Small exercises like these move the choice from a rule you have to recall into a habit that feels natural.

Final Thoughts On This Small Choice

Native speakers swap between “all their” and “all of their” without much thought, yet learners often feel stuck. Once you see that both options are grammatically sound, and that the word after “their” guides the pattern, the choice turns into a matter of tone and flow.

Rely on solid references, listen closely to how the phrases sound in real sentences, and give yourself space to experiment. With practice, you will pick the form that fits each context and write with more confidence about people, their actions, and all their shared experiences.