i'm not sure

USAGE SUMMARY

"I'm not sure" is a perfectly acceptable phrase to use in written English.
It is usually used when one is uncertain about something or is unable to answer a question. For example: I'm not sure what time the movie starts.

✓ Grammatically correct

News & Media

Science

Human-verified examples from authoritative sources

Exact Expressions

29 human-written examples

Actually, I'm not sure.

The New York Times

M: I'm not sure.

The New Yorker

What, I'm not sure.

Independent

A: I'm not sure.

The New York Times

I'm not sure yet".

The New York Times

So I'm not sure.

The New York Times

Human-verified similar examples from authoritative sources

Similar Expressions

8 human-written examples

I was not sure.

The New York Times

But I am not sure.

The Economist

○ No. ○ I am not sure.

Environmental Sciences Europe

S2: I am not sure.

Asian-Pacific Journal of Second and Foreign Language Education

I am not sure.

BMC Medical Ethics

Expert writing Tips

Best practice

In formal writing, consider more sophisticated alternatives like "I am uncertain" or "It is difficult to say" depending on the context.

Common error

Avoid relying on "I'm not sure" as a crutch. If you frequently use it, it might suggest a lack of knowledge or preparation. Instead, research the topic or offer a qualified answer when possible.

Linguistic Context

The phrase "I'm not sure" functions as a declarative statement expressing uncertainty or a lack of knowledge. Ludwig AI confirms its grammatical correctness and common usage across diverse contexts. It is frequently used to politely decline to provide a definitive answer.

Expression frequency: Very common

Frequent in

News & Media

52%

Science

32%

Academia

16%

Less common in

Formal & Business

0%

Encyclopedias

0%

Wiki

0%

Ludwig's WRAP-UP

In summary, "I'm not sure" is a grammatically correct and widely used phrase for expressing uncertainty or lack of knowledge. Ludwig AI confirms its acceptability and common occurrence across various contexts, including News & Media and Science. While suitable for most situations, more formal alternatives might be considered for strictly professional writing. When used, consider whether another option like "I'm uncertain" could be used depending on the formality of your audience.

More alternative expressions

Phrases that express similar concepts, ordered by semantic similarity:

I'm uncertain

This alternative replaces "not sure" with the single word "uncertain", maintaining a direct expression of doubt.

I'm not certain

This alternative substitutes "sure" with "certain", conveying a similar meaning of uncertainty.

I don't know for sure

This alternative adds "for sure" to emphasize the lack of certainty.

I'm doubtful

This alternative uses "doubtful" to convey a sense of uncertainty or skepticism.

I have my doubts

This alternative expresses uncertainty with a more idiomatic phrase indicating reservations.

I couldn't say

This alternative indicates an inability to provide a definite answer.

It's hard to say

This alternative suggests that providing a definitive answer is difficult.

I can't confirm

This alternative expresses an inability to verify something as true or accurate.

I'm unable to confirm

This alternative states the speaker does not have the ability to confirm something.

That's unclear to me

This alternative indicates the speaker lacks clarity on the subject.

FAQs

How can I use "I'm not sure" in a sentence?

"I'm not sure" is commonly used to express uncertainty or a lack of knowledge regarding a question or topic. For example, "I'm not sure what time the meeting starts".

What are some alternatives to "I'm not sure"?

You can use alternatives like "I'm uncertain", "I'm doubtful", or "I couldn't say" depending on the context and desired level of formality.

Is it acceptable to use "I'm not sure" in formal writing?

While grammatically correct, "I'm not sure" may be considered informal for certain types of formal writing. In such cases, consider using alternatives like "I am uncertain" or "It is difficult to say".

What's the difference between "I'm not sure" and "I don't know"?

Both phrases express a lack of knowledge, but "I'm not sure" can sometimes imply a degree of uncertainty even if you have some information, whereas "I don't know" suggests a complete lack of knowledge. The phrase "I don't know" is also more direct.