Thats or That’s: Which One Is Grammatically Correct? 

If you have ever typed a quick message and second-guessed yourself on whether to write “thats” or “that’s,” you are not alone. This small punctuation question trips up native speakers and English learners alike. The answer, however, is clear-cut. One form is correct in every situation; the other does not belong in written English at all. Knowing which is which — and understanding the rule behind it — helps you write with more confidence, whether you are sending a work email, posting on social media, or finishing an academic assignment.

This article breaks down the grammar behind the apostrophe, shows you exactly how “that’s” functions in a sentence, gives you real writing examples, and covers what major style guides say. By the time you finish reading, the correct form will feel automatic. The goal here is not just to tell you which word is right, but to make sure you never mix them up again. Every section below is grounded in standard grammar rules and confirmed by recognized authorities on English usage.

What You Need to Know Up Front: That’s Is the Correct Form in Standard English

Let’s keep this simple before we go deeper.

“Thats” — incorrect. Not a word. No exceptions.
“That’s” — correct. A standard English contraction used in all types of writing.

The difference between the two comes down to one character: the apostrophe. In English grammar, an apostrophe in a contraction marks where one or more letters have been removed when two words are joined together. Without that apostrophe, the resulting form is not a contraction — it is just a spelling error.

Think of it like a handshake between two words. When “that” and “is” come together, the “i” in “is” steps aside, and an apostrophe takes its place. Remove the apostrophe and the handshake breaks. The word “thats” is the result of that broken handshake — technically readable, but grammatically invalid. No dictionary recognizes “thats” as a standalone entry, and no style guide approves of it in any context.

“That’s” = “That Is”

The most common use of “that’s” is as a shortening of “that is.” This is the version most people think of without realizing it.

Examples:

• That’s a good point. → That is a good point.
• That’s the book I mentioned. → That is the book I mentioned.
• That’s not what I said. → That is not what I said.

Quick test: If you can replace “that’s” with “that is” and the sentence still sounds right, the contraction is being used correctly.

“That’s” = “That Has”

This use is less common but just as correct. Here, “that’s” stands in for “that has,” typically before past participles like “been,” “happened,” or “gone.”

Examples:

• That’s been the problem all along. → That has been the problem all along.
• That’s never happened before. → That has never happened before.
• That’s gone on long enough. → That has gone on long enough.

Quick test: If swapping “that’s” for “that has” works naturally, you are using the correct form.

Examples That Show the Difference Clearly

Seeing the two forms side by side makes the rule stick faster than any explanation. Here are direct comparisons. Notice how every “thats” entry signals an incomplete contraction — one that would immediately stand out to any editor or grammar-checking tool as an error.

Incorrect (Thats)	Correct (That’s)	Full Form
Thats a great idea.	That’s a great idea.	That is a great idea.
I think thats wrong.	I think that’s wrong.	I think that is wrong.
Thats been resolved.	That’s been resolved.	That has been resolved.
Thats not the answer.	That’s not the answer.	That is not the answer.
I heard thats the plan.	I heard that’s the plan.	I heard that is the plan.
Thats all for now.	That’s all for now.	That is all for now.

In each row, “thats” fails because it has no apostrophe to signal the contraction. A reader may still understand what you mean, but the form is grammatically wrong and looks careless in any professional or academic setting.

Writing Examples for Emails, Essays, and Social Media

Context matters when it comes to contractions. Here is how “that’s” fits into different types of writing, and what each example would look like if someone mistakenly dropped the apostrophe.

Professional email:

“I reviewed the report, and I believe that’s the most efficient approach given our timeline.”

Using “thats” here would immediately lower the impression of professionalism, even if the reader understands the meaning. In a business email, spelling accuracy reflects on your attention to detail.

Academic essay (used with care):

“The data suggests that’s a pattern worth examining in further research.” (Chicago and MLA both allow contractions in nontechnical academic writing when tone supports it.)

Some academic writers still prefer to expand the contraction — “that is” — to maintain a stricter formal register. Either version is acceptable in most humanities contexts, but “thats” without the apostrophe is never acceptable.

Social media caption:

“Just finished my first 5K — that’s something I never thought I’d say!”

Social media posts are casual by nature, but that does not mean spelling rules disappear. Readers notice sloppy contractions even in informal posts.

Text message:

“That’s perfect, see you at 6.”

Blog post intro:

“That’s exactly the question this guide is designed to answer.”

In all five examples, replacing “that’s” with “thats” would introduce a spelling error. The apostrophe is non-negotiable regardless of the platform or audience.

Tables of Common Contractions and What They Omit

Understanding how contractions work in general helps reinforce why “that’s” always needs its apostrophe. English uses contractions across many word combinations, and the rule is consistent: every contraction marks what was removed with an apostrophe. The tables below show some of the most common contractions grouped by what they omit. Once you see the pattern, “thats” without an apostrophe becomes obviously wrong.

Contractions with “is”

Contraction	Full Form	Letters Removed
That’s	That is	i
It’s	It is	i
He’s	He is	i
She’s	She is	i
What’s	What is	i
Here’s	Here is	i

Contractions with “has”

Contraction	Full Form	Letters Removed
That’s	That has	ha
It’s	It has	ha
He’s	He has	ha
She’s	She has	ha

Contractions with “not”

Contraction	Full Form	Letters Removed
Don’t	Do not	o
Can’t	Cannot	no
Won’t	Will not	ill + o
Isn’t	Is not	o
Wasn’t	Was not	o

Every single contraction in standard English uses an apostrophe to mark what is missing. “Thats” breaks this rule by dropping the apostrophe, which makes it incorrect by definition.

Practical Rules and Memory Tricks — Fast and Useful

You do not need to memorize a grammar handbook to get this right. A few simple techniques are enough, and most of them take less than five seconds to apply.

Rule 1: The substitution test
Before writing “that’s,” try replacing it with “that is” or “that has.” If the sentence still makes sense, the apostrophe belongs. If neither replacement works, you probably do not need “that’s” at all. This test works in almost every situation you will encounter.

Rule 2: Apostrophe = something is missing
Every time you see or write an apostrophe in a contraction, remind yourself: something was left out. The apostrophe is a placeholder for those missing letters. “Thats” without an apostrophe is claiming nothing was removed — which cannot be true if you are combining two words.

Rule 3: Read it aloud
Say the sentence out loud using “that is.” If your spoken version naturally uses “that is,” then the written version needs the apostrophe. This works for virtually all contractions, not just “that’s.” Most people do not say “thats” aloud — they say “that is” or “that’s.” Let your ear guide your fingers.

Rule 4: Treat all contractions the same way
The same rule that applies to “that’s” applies to “it’s,” “he’s,” “she’s,” “what’s,” and dozens of other contractions. If you get in the habit of always including the apostrophe in contractions, the “thats” error disappears automatically.

Memory trick:
Think of the apostrophe as a small hook that holds two words together. Without the hook, the words fall apart and the meaning is lost. “Thats” has no hook — so it cannot hold anything together grammatically. Attach the hook, and the word works correctly every time.

Common Errors and How to Fix Them (With Quick Edits)

Here are the most frequent mistakes writers make with this contraction, along with fast corrections. Each error has a specific cause, which is worth understanding so you can avoid it rather than just fixing it after the fact.

Error 1: Dropping the apostrophe when typing fast

• ❌ “Thats great news!”
• ✅ “That’s great news!”
  Cause: Speed. The apostrophe key requires a deliberate keystroke on most keyboards, and fast typists often skip it.
  Fix: Slow down on contractions. Enable autocorrect if your platform supports it, but always proofread manually.

Error 2: Confusing “that’s” with “thats” in informal writing

• ❌ “I think thats what she meant.”
• ✅ “I think that’s what she meant.”
  Cause: The mistaken belief that informal writing does not require correct spelling.
  Fix: Informal tone does not mean incorrect spelling. Even casual writing benefits from getting contractions right.

Error 3: Using “its” instead of “it’s” (a parallel mistake)

• ❌ “Its a good idea that thats included.”
• ✅ “It’s a good idea that that’s included.”
  Fix: Both “it’s” and “that’s” need apostrophes. Keep them consistent.

Error 4: Assuming autocorrect will catch it
Some devices will autocorrect “thats” to “that’s,” but not all do — and relying on autocorrect without checking is a risky habit, especially in formal documents where an uncorrected error can affect how readers perceive your competence.

Error 5: Overusing contractions in formal writing

• ❌ (in a legal contract) “It is agreed that’s the final term.”
• ✅ (in a legal contract) “It is agreed that this is the final term.”
  Fix: In formal legal or technical documents, expand contractions entirely. The issue here is not just the spelling — it is the register.

Quotes from Authorities

Several recognized grammar and style authorities offer clear positions on contractions.

The Chicago Manual of Style (18th ed.) states: “Most types of writing benefit from the use of contractions. If used thoughtfully, contractions in prose sound natural and relaxed and make reading more enjoyable.”

The Modern Language Association (MLA) confirms that it allows contractions in its publications and notes they are easier to read and sound more natural, while acknowledging that very formal research writing may call for their omission.

The Associated Press Stylebook calls contractions reflective of informal speech and writing, advising writers to avoid excessive use rather than banning them altogether.

Cambridge Dictionary notes that the use of contractions in formal writing is generally not acceptable — reinforcing that context drives the decision, not grammar itself.

The one point all authorities agree on: when a contraction is used, it must be spelled correctly. That means “that’s,” always — never “thats.”

The Role of Style Guides: When to Use or Avoid That’s

Knowing the correct spelling is step one. Knowing when to use the contraction at all is step two.

Style Guide	Position on Contractions	Best Context for “That’s”
Chicago Manual of Style	Allowed; use thoughtfully	Books, essays, blog posts, trade writing
AP Stylebook	Allowed; avoid excessive use	News writing, marketing copy
MLA	Allowed in most writing	Humanities essays, nontechnical academic work
APA	Generally discouraged	Avoid in formal research papers, theses
Cambridge Dictionary	Not acceptable in formal writing	Casual or semi-formal contexts only

Summary for writers:

• Use “that’s” freely in blog posts, emails, social media, and conversational writing.
• Use it with care in academic essays — acceptable in many humanities fields, but always check your instructor’s or journal’s specific requirements.
• Avoid it in legal contracts, scientific papers, dissertations, and any document where a strictly formal register is expected.
• When in doubt, write “that is” or “that has” — the full form is always grammatically correct regardless of context.
• Never write “thats” under any circumstances in any context. This is the one rule without exceptions.

One nuance worth knowing: even style guides that allow contractions do not mean anything goes. The AP Stylebook, for example, recommends contractions that reflect natural speech but warns against excessive use, especially when quoting sources. The takeaway is that “that’s” is a tool — a useful one — but like any tool, it works best when used deliberately.

A Short Checklist Editors and Writers Should Use

Before submitting or publishing any piece of writing, run through this checklist to catch contraction errors. It takes under a minute and prevents a mistake that can undermine reader trust — especially in professional or published content.

• [ ] Have I used “that’s” (with apostrophe) every time I mean “that is” or “that has”?
• [ ] Have I run a find-and-replace for “thats” (without apostrophe) to catch any typos?
• [ ] Does the level of formality in the document actually allow contractions?
• [ ] Have I checked all similar contractions — it’s, he’s, she’s, what’s — for the same apostrophe error?
• [ ] Did I test any unclear “that’s” by substituting “that is” or “that has” to verify the meaning?
• [ ] If the document is formal (legal, medical, academic), have I replaced all contractions with their full forms?
• [ ] Have I avoided relying entirely on autocorrect to catch these errors?

Working through this list once before hitting publish or send is enough to catch the most common apostrophe mistakes. For longer documents, consider using a grammar tool as a first pass, but always follow up with manual proofreading.

Closing: Small Punctuation, Big Difference

One apostrophe. That is all it takes to move from a spelling error to correct standard English. “Thats” carries no grammatical weight in any recognized variety of English. It has no definition, no function, and no place in writing that is meant to be taken seriously.

“That’s,” on the other hand, does real work in a sentence. It shortens “that is” or “that has,” keeps your writing flowing naturally, and signals that you understand how contractions operate. That small curved mark is not decoration — it is meaning.

References and Further Reading

• The Chicago Manual of Style, 18th Edition — University of Chicago Press
• The Associated Press Stylebook — Associated Press
• MLA Handbook, 9th Edition — Modern Language Association
• Publication Manual of the American Psychological Association, 7th Edition
• Cambridge Dictionary — contractions in formal writing
• Merriam-Webster Dictionary — entry on contractions
• Grammarhow.com — Thats vs. That’s
• GrammarPaths.com — That’s or Thats
• GrammarLearns.com — Thats or That’s

Frequently Asked Questions

Is “Thats” Ever Correct?

No. “Thats” without an apostrophe is always incorrect in standard English grammar and all recognized writing contexts.

What Does “That’s” Mean?

“That’s” is a contraction meaning either “that is” or “that has,” depending on the sentence context and what follows it.

Why Do People Mix Up “Thats” and “That’s”?

Fast typing, autocorrect failures, and limited understanding of contraction punctuation rules cause this common and easy-to-fix mistake.

How Can I Remember the Difference Easily?

Replace “that’s” with “that is” aloud. If it fits, use the apostrophe. No apostrophe means no contraction exists.

Does Using the Wrong Form Matter?

Yes. Incorrect spelling damages credibility, reduces clarity, and signals poor attention to grammar in professional or academic writing.

Conclusion

The answer to “thats or that’s which is correct?” is straightforward: it is always “that’s,” with an apostrophe. “Thats” without the apostrophe is a misspelling with no place in standard English, regardless of how casual or informal the writing is. The apostrophe represents the missing letters that make the contraction work, and without it, the word simply does not function.

Getting this right is not about being a grammar expert. It is about paying attention to one character that changes everything. Whether you are writing a caption, a report, or a quick reply, the rule stays the same. Use “that’s,” check for it before you publish, and you will not have to think about it again.