How to Express Doubt in English

How to Express Doubt in English (A Complete Guide for B1–C1 Learners)

How to Express Doubt in English

Hello, dear English learners! Today, we’re exploring one of the most useful communication skills: expressing doubt. Whether you’re taking part in a discussion, responding to a suggestion, or politely questioning someone’s opinion, knowing how to express doubt helps you sound thoughtful, polite, and confident. How to Express Doubt in English

These expressions are especially helpful in conversations, debates, workplace communication, and Cambridge exam tasks. Let’s look at a wide range of phrases you can use to show uncertainty, hesitation, scepticism, or polite disagreement — all with natural examples.

Useful Phrases to Express Doubt in English

I’m not sure / I’m not certain

Meaning: A gentle and polite way to show uncertainty.

• I’m not sure Jill should marry David; she still seems unsure about the whole idea.
• I’m not certain your calculations are correct — we may need to check them again.
• I’m not quite sure whether this is the right solution.

I’m not convinced

Meaning: You don’t fully believe or accept an idea.

• I’m not convinced this plan will work in the long run.
• I’m not entirely convinced that Mary is suitable for this position.

As far as I know

Meaning: You believe something is true, but you may be wrong. How to Express Doubt in English

• As far as I know, Michael still hasn’t returned from London.
• As far as I know, the meeting is scheduled for tomorrow — but double-check, just in case.

I have a doubt / I have my doubts

Meaning: You are unsure or sceptical about something.

• I have a doubt that we’ll finish this project before Friday.
• You may be right, but I still have my doubts.

I’m hesitant to believe

Meaning: Used when you don’t fully trust or accept something.

• I’m hesitant to believe that the prices will drop any time soon.
• The president is hesitant to believe that the peace agreement will last.

I’m doubtful about…

Meaning: You feel uncertain or unconvinced about a situation.

• Helen liked the suggestion, but I’m doubtful about it.
• I’m doubtful about whether we’ll ever find our missing dog.

I’m not confident

Meaning: You don’t feel certain or optimistic about an outcome. How to Express Doubt in English

• The company was not confident about meeting the quarterly targets.
• I’m not confident about the success of these negotiations.

As likely as not

Meaning: Means probably, often used for predictions.

• As likely as not, Monica has forgotten about her promise to help us move.
• The case will, as likely as not, end up in court.

In doubt / Doubtful

Meaning: Shows uncertainty or hesitation.

• Fiona was in doubt about whether to call her lawyer.
• Mark was doubtful about signing another contract.

Check up on (something/someone)

Meaning: To verify information because you’re uncertain.

• The journalist phoned to check up on the details of the accident.
• The doctor visited daily to check up on the patient.

Bonus Higher-Level Phrases (B2–C1)

These expressions are perfect for more formal conversations and exam writing tasks.

I have reservations about…

Meaning: You have concerns or serious doubts. How to Express Doubt in English

• I have reservations about moving the deadline forward again.
• She has reservations about investing such a large amount of money.

I’m not entirely convinced that…

Meaning: A polite but firm way to show doubt.

• I’m not entirely convinced that this strategy is sustainable.
• I’m not entirely convinced that we should trust their proposal.

Something doesn’t quite add up

Meaning: Something feels unclear, suspicious, or illogical.

• His explanation doesn’t quite add up — I feel he’s hiding something.
• The numbers don’t quite add up; we must have made a mistake somewhere.

I find it hard to believe…

Meaning: You struggle to accept something as true.

• I find it hard to believe they made that decision without consulting us.
• I find it hard to believe she finished the entire project in one day.

I’m sceptical about…

Meaning: You doubt that something is true or effective.

• I’m sceptical about the benefits of this new policy.
• Many employees are sceptical about the promised changes.

Expressing doubt is an important communication skill — it helps you show critical thinking, stay polite, and take part in meaningful discussions. Try using these phrases in your daily conversations, writing tasks, or speaking practice.

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