I'm not sure

USAGE SUMMARY

The phrase "I'm not sure" is correct and usable in written English.
It can be used in any context to express uncertainty or doubt. For example, "I'm not sure whether I should order the steak or the salmon for dinner tonight."

✓ Grammatically correct

News & Media

Science

Human-verified examples from authoritative sources

Exact Expressions

60 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

I'm not sure, either.

The New Yorker

I'm not sure which.

Independent

"But I'm not sure".

The New York Times

"Because I'm not sure.

The New York Times

"I'm not sure what.

The New York Times - Health

Expert writing Tips

Best practice

Use "I'm not sure" to express uncertainty or lack of knowledge politely and directly. It's suitable for both formal and informal settings.

Common error

Avoid overuse of "I'm not sure" in close proximity. Variety improves writing quality. Consider using alternatives like "I'm uncertain" or "I don't know for sure" to maintain reader engagement.

Linguistic Context

The phrase "I'm not sure" primarily functions as a declarative statement expressing uncertainty, doubt, or lack of knowledge. Ludwig AI confirms its correct usage. It indicates a speaker's inability to provide a definitive answer or opinion.

Expression frequency: Very common

Frequent in

News & Media

61%

Science

21%

Formal & Business

1%

Less common in

Encyclopedias

0%

Wiki

1%

Reference

0%

Ludwig's WRAP-UP

In summary, the phrase "I'm not sure" is a grammatically sound and exceedingly common expression used to convey uncertainty or a lack of knowledge. Ludwig AI confirms the phrase's correctness and broad applicability. Its neutral register makes it suitable for diverse contexts, from casual conversations to professional communications. While prevalent in both speech and writing, overuse should be avoided by incorporating semantically similar alternatives, such as "I'm uncertain" or "I don't know for sure".

More alternative expressions

Phrases that express similar concepts, ordered by semantic similarity:

I'm not really sure

Adds slight emphasis or hesitation.

I'm uncertain about that

Specifies the subject of uncertainty.

I'm a bit unsure

Implies a mild level of uncertainty.

I don't know for sure

Adds emphasis on the lack of certainty.

I am uncertain

More formal alternative, suitable for professional or academic contexts.

I couldn't say

More indirect way to express uncertainty.

It's hard to say

Shifts the focus to the difficulty of knowing.

I have my doubts

Expresses a stronger sense of skepticism.

I'm not entirely convinced

Expresses doubt or incomplete belief.

I'm just guessing

Suggests a lack of knowledge and reliance on conjecture.

FAQs

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

You can use "I'm not sure" to express uncertainty about a fact, decision, or future event. For example, "I'm not sure if I can make it to the party tonight" or "I'm not sure which option is best".

What can I say instead of "I'm not sure"?

You can use alternatives like "I'm uncertain", "I don't know for sure", or "I have my doubts" depending on the context and the level of uncertainty you want to convey.

Is it correct to say "I am not sure" instead of "I'm not sure"?

Yes, both phrases are grammatically correct. "I'm not sure" is a contraction and is more common in everyday conversation and informal writing. "I am not sure" is slightly more formal and can be used in more formal writing or when you want to emphasize the statement.

What's the difference between "I'm not sure" and "I'm unsure"?

The phrases "I'm not sure" and "I'm unsure" are very similar in meaning and can often be used interchangeably. "I'm unsure" might imply a slightly stronger feeling of uncertainty or hesitation, but the difference is subtle.