18 Different Ways to Say “I Don’t Know” in English

Key takeaways:

• There are many common ways to say “I don’t know” in English, the key difference being their levels of formality.
• In this article, we are exploring what to say instead of “I don’t know” to express uncertainty in English, according to the context you want to express yourself in.
• Phrases like “I’m not sure” and “I have to check it” are ideal if you are wondering how to say “I don't know” professionally, while “beats me” and “IDK” are funny ways to say “I don’t know” in casual conversations.
• Using the right phrase for each situation helps you sound natural and confident when speaking English.

“I don’t know” is the standard and most direct way to express uncertainty in English. But did you know there are at least 18 different ways to say it?

Depending on the context, whether you’re in a business meeting, chatting with a friend, or caught off guard by a random question, you can choose a phrase that sounds more natural and appropriate.

In this guide, you’ll learn how to say “I don’t know” in English across different situations, from polite and professional to informal and playful. Let’s get started!

How to Say “I Don’t Know” in English: 18 Useful Expressions

1. I don’t know

Meaning: The most basic and universal way to say “I don’t know.” It fits almost any situation — casual or formal. It’s neutral, simple, and always correct.

Example:

• A: What time does the store close?
• B: I don’t know, maybe around 9 PM.

2. I’m not sure

Meaning: A softer and more polite way to say “I don’t know.” Perfect for work situations or whenever you want to sound less definite.

Example:

• A: Will the project be ready by Friday?
• B: I’m not sure, but I’ll check with the team.

3. I'm not the best person to answer that

Meaning: “I’m not the right person to answer this question.” Professional, diplomatic, and respectful — great for meetings or emails when a question is outside your area of expertise.

Example:

• A: Can you explain how the new software integrates with our system?
• B: I’m not the best person to answer that. You should talk to the IT team.

4. I have to check it

Meaning: “I need to verify or look it up.” This is a proactive way to say you don’t know something right now but will find out. Perfect for professional settings.

Example:

• A: How many units do we have in stock?
• B: I have to check it and get back to you.

5. I'll find out and tell you

Meaning: “I’ll discover the answer and share it with you.” This sounds active, helpful, and responsible, suitable for work or everyday life.

Example:

• A: Do you know if the restaurant accepts credit cards?
• B: I’ll find out and tell you before we go.

6. I have no idea

Meaning: “I really have no clue.” This phrase shows stronger emphasis than “I don’t know.” It means you truly have no information or guess about something. Great for casual conversations or relaxed professional settings, honest but polite.

Example:

• A: Why is the internet so slow today?
• B: I have no idea. It was working fine this morning.

7. I can't remember

Meaning: “I don’t recall right now.” Use this when the information is somewhere in your memory, but you just can’t access it at the moment. Softer and friendlier than saying “I don’t know.”

Example:

• A: What was the name of that Italian restaurant we went to last month?
• B: I can’t remember. It started with an M, I think.

8. What I do know is...

Meaning: “What I can tell you is…” A smart way to stay positive in conversation. Even if you don’t have the full answer, you share what you do know. Great for meetings or presentations, as it keeps you sounding confident and helpful.

Example:

• A: Do you know exactly when the new product will launch?
• B: What I do know is that it’ll be sometime in Q3.

9. I don't have the slightest idea

Meaning: “I have absolutely no idea.” A dramatic (but funny) way to say you’re completely lost. More expressive than “I have no idea.” Use it casually with friends.

Example:

• A: How does quantum physics actually work?
• B: I don’t have the slightest idea. That’s way over my head.

10. I'm clueless

Meaning: “I have no idea / I’m lost.” Very casual and slightly self-ironic, perfect among friends. It shows you’re relaxed about not knowing something. Avoid it in formal settings.

Example:

• A: How do I fix this error on my computer?
• B: I’m clueless about tech stuff. You should ask David.

11. No clue

Meaning: “No idea / Not sure.” A short, snappy version of “I have no clue.” Super informal, best for texts or quick chats.

Example:

• A: What time is Jake arriving?
• B: No clue. He didn’t text me.

12. Beats me

Meaning: “No idea / Who knows?” An informal, idiomatic phrase that sounds like you’re shrugging. Fun and very common in spoken English.

Example:

• A: Why did they cancel the concert?
• B: Beats me. I was really looking forward to it.

13. Who knows?

Meaning: “Nobody knows! / Hard to say.” Used when something is uncertain or unpredictable. A little philosophical, a little casual — great for light conversation.

Example:

• A: Do you think we’ll have flying cars in 20 years?
• B: Who knows? Technology changes so fast.

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14. Now you got me

Meaning: “You got me there / You stumped me.” Playful and lighthearted, great when someone surprises you with a tough or random question.

Example:

• A: What’s the capital of Kazakhstan?
• B: Now you got me. I have no idea!

15. How would I know?

Meaning: “How could I possibly know that?” Sounds slightly defensive, it’s used when someone expects you to know something you realistically wouldn’t. Be careful with your tone; it can come across as irritated.

Example:

• A: What’s going on in their meeting?
• B: How would I know? I’m not in there.

16. How should I know?

Meaning: “Why would I know that?” Similar to “How would I know?” but a little sharper. Common among close friends or family when you’re frustrated or teasing.

Example:

• A: Where did Mom put my backpack?
• B: How should I know? Ask her yourself!

17. I dunno

Meaning: “I don’t know (very casual)”. Another word for IDK, it’s a lazy, spoken contraction you’ll hear all the time in real life. Super relaxed — perfect for friends or informal chats.

Example:

• A: What do you want for dinner?
• B: I dunno, whatever.

18. IDK

Meaning: “I don’t know” (text slang). The internet abbreviation for “I don’t know.” You’ll see it everywhere online — in texts, social media, or gaming chats.

Example:

• A: What time are we meeting tomorrow?
• B: IDK, maybe around 3?

Learn How to Say “I Don’t Know” Professionally and More English Vocabulary with Promova

Now that you no longer have to wonder what to say instead of “I don’t know” and how to say “I don’t know” professionally in English, you can make a big difference in the way you communicate — especially in meetings, presentations, or interviews.

With Promova, you can learn English the smart way. Our quick, personalized lessons teach practical business vocabulary and everyday phrases you’ll actually use. You can also practice realistic conversations with AI, so you’ll never have to worry about making mistakes.

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Conclusion

Now you know 18 other ways to say “I don’t know” professionally, and even a few funny and intelligent alternatives that make you sound more fluent and natural in English.

From a polished “I’m not sure” during a meeting to a relaxed “IDK” with friends, you’re ready for any context.

Remember — admitting you don’t know something isn’t a weakness. It’s a sign of honesty, curiosity, and self-awareness. And with Promova, you can keep learning, growing, and expanding your English vocabulary every day.