22 Japanese ways to say “I’m not sure”

Learning how to express uncertainty in Japanese can really boost your conversational skills. It’s a subtle art, and there are plenty of ways to say “I’m not sure” that fit different moods and situations.

Whether you’re chatting casually with friends or speaking more formally, having a range of phrases helps you sound natural and polite. Plus, it makes your Japanese richer and more versatile.

In this list, we’ll explore 22 expressions that cover everything from casual doubts to formal hesitations. Each one is easy to remember and practical for day-to-day use.

Understanding these phrases will help you navigate conversations with confidence, especially when you don’t have all the answers. It’s all about sounding genuine and approachable.

By the end, you’ll have a handy toolkit of expressions to keep your Japanese flowing smoothly, no matter how uncertain you feel.

Ready to dive in? Let’s start exploring these warm, relatable ways to say “I’m not sure” in Japanese!

Getting Comfortable with Uncertainty

Expressing doubt or uncertainty is a natural part of any language. Japanese offers many subtle ways to do this, depending on how casual or formal you want to be.

Some expressions soften your uncertainty, while others are more direct. Knowing which one to use can make your conversations feel more authentic and respectful.

In Japanese culture, humility and politeness are key, so these phrases often include gentle words that show you’re thoughtful about your response.

Sometimes, having a great beginner phrasebook can give you a perfect starting point for a cohesive understanding.

It’s all about getting comfortable with these expressions bit by bit.

Next, we’ll start with some casual ways to say “I’m not sure” that you can use with friends or in relaxed settings.

Part 1: Casual Suggestions

1. 行けたら行く (Iketara iku) – “I’ll come if I can.”

This phrase literally means “If I can go, I’ll go.” It’s a casual way to express uncertainty about your plans.

It’s easy to use when you want to politely indicate you’re unsure whether you’ll attend an event or not. Just remember that “行けたら” (Iketara) means “if I can go,” and “行く” (Iku) means “I’ll go.”

A great thing about this phrase is that it sounds friendly and non-committal but still shows willingness.

It’s perfect for casual invites when you want to keep it open-ended.

You might also hear “多分行く” (Tabun iku) meaning “I’ll probably go,” which is similar but less uncertain.

Use this to keep your options open without sounding rude or unsure of yourself.

2. どうかな (Dou kana) – “I wonder.”

“どうかな” (Dou kana) literally means “I wonder” or “I’m not sure.” It’s a casual, soft way to express doubt or hesitation.

It’s easy to remember because “どう” means “how” or “what,” and “かな” is a sentence-ending particle that adds uncertainty, like “I wonder.”

This phrase works well in conversations when you want to gently express that you don’t have a clear answer.

Be careful not to use it in very formal situations as it’s quite informal.

For example, if someone asks if a restaurant is good, you can reply “どうかな” to mean “I’m not sure.”

It’s a handy phrase to sound natural and relatable.

3. わからないかも (Wakaranai kamo) – “Maybe I don’t know.”

“わからないかも” (Wakaranai kamo) combines “わからない” (I don’t know) with “かも” (maybe), adding a gentle uncertainty.

It’s a friendly way to say you’re unsure without sounding blunt or negative.

“かも” (kamo) is a great word to soften statements and is used in everyday speech.

It’s a useful phrase when you want to share your doubt but keep the tone light.

You can also use it with other verbs, like “できないかも” (I might not be able to).

Try using this one when you want to express hesitance but still be polite.

4. たぶん違うと思う (Tabun chigau to omou) – “I think it’s probably different.”

“たぶん違うと思う” (Tabun chigau to omou) is a casual way to express a probable but uncertain opinion.

“たぶん” means “probably,” “違う” means “different” or “wrong,” and “と思う” means “I think.”

This phrase is great when you want to say “I’m not sure, but I think it’s probably not right.”

It’s less direct and softer than just saying “違う” (It’s wrong).

Be mindful it carries a nuance of polite doubt, so it’s perfect for friendly conversations.

Using “と思う” (I think) is a great tip for softening your statements.

5. どうだろう (Dou darou) – “I wonder how it is.”

“どうだろう” (Dou darou) is a casual phrase that means “I wonder” or “I’m not sure.”

“どう” means “how,” and “だろう” is a soft conjectural ending like “I guess” or “I wonder.”

It’s commonly used when you want to express uncertainty but keep the tone curious rather than negative.

It’s a bit more thoughtful than simply saying “わからない.”

Be aware it’s mostly used in casual or semi-formal contexts.

Try it when you want to sound reflective and open-minded.

6. ちょっと分からない (Chotto wakaranai) – “I don’t really know.”

“ちょっと分からない” (Chotto wakaranai) literally means “I don’t really know,” with “ちょっと” adding a softening effect.

It’s perfect to use when you want to admit your uncertainty in a gentle, non-committal way.

“ちょっと” means “a little” or “a bit,” which helps to tone down your expression.

This phrase is casual but polite enough for everyday conversation.

It’s a subtle way to say you’re unsure without feeling pressured to have a definite answer.

Use this when you want to keep things light but honest.

7. まだ決めてない (Mada kimetenai) – “I haven’t decided yet.”

“まだ決めてない” (Mada kimetenai) means “I haven’t decided yet,” which is a great way to express uncertainty about your choice.

“まだ” means “still” or “not yet,” and “決めてない” is the negative form of “decide.”

This phrase is casual but clear and honest.

It’s useful when someone asks for your opinion but you haven’t made up your mind.

Using “まだ” helps to convey that your uncertainty might change soon.

Try this one to sound transparent and thoughtful.

8. ちょっと自信がない (Chotto jishin ga nai) – “I’m a bit unsure/confident.”

“ちょっと自信がない” (Chotto jishin ga nai) means “I’m a bit unsure” or “I lack confidence.”

“自信” (jishin) means “confidence,” and “ない” means “not have.”

This phrase expresses doubt about your own knowledge or ability, not just facts.

It’s perfect when you want to admit uncertainty but also show humility.

It’s a very relatable phrase that many learners find useful.

Use it to express honest feelings about your certainty level.

Part 2: Polite & Formal Suggestions

9. はっきり分かりません (Hakkiri wakarimasen) – “I don’t know clearly.”

“はっきり分かりません” (Hakkiri wakarimasen) is a polite way of saying “I don’t know clearly” or “I’m not certain.”

“はっきり” means “clearly,” and “分かりません” is the negative polite form of “to understand.”

This phrase is perfect for formal or business contexts where you want to admit uncertainty politely.

It’s stronger than casual “わからない” but still humble.

Use this when you want to be respectful but honest about your limitations.

It works well in meetings or formal emails.

10. よく分かりかねます (Yoku wakari kanemasu) – “I’m afraid I don’t quite understand.”

“よく分かりかねます” (Yoku wakari kanemasu) is a very polite and humble way to say “I don’t quite understand.”

“よく” means “well,” and “分かりかねます” is a humble negative expression for “understand.”

This phrase is often used in customer service or formal situations.

It expresses uncertainty with respect and deference.

Be sure to use it only in formal contexts to avoid sounding awkward.

It’s a great phrase to keep handy for professional conversations.

11. 確信が持てません (Kakushin ga motemasen) – “I can’t be certain.”

“確信が持てません” (Kakushin ga motemasen) means “I can’t be certain.”

“確信” means “certainty,” “持てません” is the polite negative form of “to hold.”

This phrase is good for formal discussions when you want to admit your doubt explicitly.

It sounds professional and thoughtful.

Use this phrase to express careful hesitation.

It’s ideal for situations requiring tact and precision.

12. まだ調査中です (Mada chousa chuu desu) – “It’s still under investigation.”

“まだ調査中です” (Mada chousa chuu desu) means “It’s still under investigation.”

“まだ” means “still,” “調査中” means “under investigation,” and “です” makes it polite.

This phrase is perfect in formal or business situations where information is incomplete.

It’s a respectful way to say you don’t have a definite answer yet.

You can use it in emails or meetings.

It helps keep expectations clear and professional.

13. 断言できません (Dangen dekimasen) – “I can’t assert it.”

“断言できません” (Dangen dekimasen) means “I can’t assert or declare it.”

It’s a formal expression used to politely admit you can’t give a confident answer.

“断言” means “assertion,” and “できません” is the negative potential form of “can do.”

This phrase is useful when you want to be very clear about your uncertainty.

It’s often used in professional or academic contexts.

Use this to sound cautious and respectful.

14. 確かではありません (Tashika dewa arimasen) – “It’s not certain.”

“確かではありません” (Tashika dewa arimasen) means “It’s not certain.”

It’s a polite way to express that the information is not definite.

“確か” means “certain,” and “ではありません” is the polite negative form of “is.”

Use this phrase in formal or written Japanese.

It’s a good phrase for careful communication.

It helps you sound precise without sounding too blunt.

15. はっきり申し上げられません (Hakkiri moushiageraremasen) – “I can’t say clearly.”

“はっきり申し上げられません” (Hakkiri moushiageraremasen) is an extremely polite way to say “I can’t clearly say.”

“申し上げる” is the humble form of “to say,” and “られません” is a potential negative ending.

This phrase shows deep respect while expressing uncertainty.

It’s best reserved for very formal or business settings.

Using humble language like this can impress your Japanese colleagues or clients.

Try this when you want to be extra careful with your words.

16. 詳細は分かりかねます (Shousai wa wakari kanemasu) – “I’m afraid I don’t know the details.”

“詳細は分かりかねます” (Shousai wa wakari kanemasu) means “I’m afraid I don’t know the details.”

It’s a polite and humble way to admit you lack specific information.

“詳細” means “details,” and “分かりかねます” is a humble negative form of “to understand.”

This phrase is useful in customer service or formal queries.

It shows professionalism and respect.

Use it when you want to handle uncertainty gracefully.

Part 3: Very Casual / Native-like Expressions

17. どうだろね (Dou daro ne) – “I wonder, huh?”

“どうだろね” (Dou daro ne) is a very casual, almost slangy way to say “I wonder” or “I’m not sure.”

It’s often heard among close friends or in informal chat.

“だろ” is a casual conjectural ending, and “ね” adds a friendly tone.

This phrase is perfect when you want to sound laid-back and natural.

Use it only with people you know well.

It’s a fun way to blend uncertainty with casual friendliness.

18. うーん、わかんない (Uun, wakannai) – “Hmm, I don’t know.”

“うーん、わかんない” (Uun, wakannai) is a very casual and natural way to say “Hmm, I don’t know.”

“うーん” is an onomatopoeia for thinking or hesitation, and “わかんない” is a casual contraction of “わからない.”

This phrase is common among young people and informal conversations.

It sounds genuine and relaxed.

Try it when you want to show honest hesitation in a friendly way.

It’s a phrase that makes you sound like a native speaker.

19. どうしようかな (Doushiyou kana) – “What should I do, I wonder?”

“どうしようかな” (Doushiyou kana) means “What should I do, I wonder?”

“どうしよう” means “what to do,” and “かな” adds uncertainty.

This phrase is a casual way to express indecision or doubt about your next step.

It’s perfect for daily life situations where you’re weighing options.

Use it to sound thoughtful and natural.

It’s a friendly and relatable expression.

20. それはどうかな (Sore wa dou kana) – “I’m not sure about that.”

“それはどうかな” (Sore wa dou kana) means “I’m not sure about that.”

“それは” means “that,” and “どうかな” expresses doubt.

This phrase is casual but a little skeptical.

It’s great when you want to politely disagree or express uncertainty.

Use it carefully so it doesn’t sound too negative.

It’s a useful phrase for friendly debates or light disagreements.

21. まだわかんないや (Mada wakannai ya) – “I still don’t know.”

“まだわかんないや” (Mada wakannai ya) is a very casual, youthful way to say “I still don’t know.”

“まだ” means “still,” “わかんない” is casual for “don’t know,” and “や” adds a soft ending used in some dialects.

It’s very informal and friendly.

Use it among close friends or in relaxed settings.

It’s perfect for expressing ongoing uncertainty in a playful way.

It helps you sound approachable and casual.

22. まあ、わからないね (Maa, wakaranai ne) – “Well, I don’t know.”

“まあ、わからないね” (Maa, wakaranai ne) means “Well, I don’t know.”

“まあ” is a filler word like “well,” “わからない” means “don’t know,” and “ね” adds a friendly tone.

This phrase is casual and expresses uncertainty with a relaxed attitude.

It’s great for conversations where you want to sound easygoing about not knowing.

Use it to keep things light and friendly.

It’s a perfect phrase to end your uncertain thoughts with warmth.

Concluding Thought

Expressing uncertainty in Japanese is a rich and nuanced skill that adds depth to your conversations. Each phrase carries its own flavor, from casual doubts to formal hesitations.

By learning these 22 expressions, you’re not just saying “I’m not sure”—you’re connecting more genuinely with others and showing your thoughtfulness.

So don’t worry about always having the perfect answer. Embrace uncertainty with these warm, natural phrases and enjoy the journey of learning Japanese!