かもしれない vs だろう vs でしょう: Japanese Probability Expressions

Understanding the difference between かもしれない (kamoshirenai),だろう (darou), and でしょう (deshou) is one of the most important distinctions in Japanese grammar. This comprehensive guide will help you master when and how to use each one correctly.

Grammar Point A

かもしれない (kamoshirenai)

Might / May / Perhaps (low-medium certainty)

Expresses possibility with uncertainty. The speaker acknowledges something could be true but isn't sure. Often used when the speaker has limited information.

Formation: Plain form + かもしれない / Noun + かもしれない / な-adj + かもしれない

Grammar Point B

だろう (darou)

Probably / I suppose / Right? (medium-high certainty, casual)

Expresses the speaker's conjecture or expectation. Higher certainty than かもしれない. Also used as a tag question seeking agreement. Casual/masculine tone.

Formation: Plain form + だろう / Noun + だろう / な-adj + だろう

Grammar Point C

でしょう (deshou)

Probably / I think / Right? (medium-high certainty, polite)

Polite form of だろう. Used in polite speech, weather forecasts, and when seeking polite agreement. Common in formal situations.

Formation: Plain form + でしょう / Noun + でしょう / な-adj + でしょう

Quick Comparison Table

Aspect	かもしれない	だろう	でしょう
Meaning	Might / May / Perhaps (low-medium certainty)	Probably / I suppose / Right? (medium-high certainty, casual)	Probably / I think / Right? (medium-high certainty, polite)
Usage	Expresses possibility with uncertainty. The speaker acknowledges something could be true but isn't sure. Often used when the speaker has limited information.	Expresses the speaker's conjecture or expectation. Higher certainty than かもしれない. Also used as a tag question seeking agreement. Casual/masculine tone.	Polite form of だろう. Used in polite speech, weather forecasts, and when seeking polite agreement. Common in formal situations.
Formation	Plain form + かもしれない / Noun + かもしれない / な-adj + かもしれない	Plain form + だろう / Noun + だろう / な-adj + だろう	Plain form + でしょう / Noun + でしょう / な-adj + でしょう
JLPT Level	N4	N4	N4
Meaning	Might / Perhaps	Probably (casual)	Probably (polite)
Certainty	30-50%	60-80%	60-80%
Formality	Neutral	Casual	Polite
Tag question?	No	Yes (だろう？)	Yes (でしょう？)
Weather forecast	Rare	Rare	Standard
JLPT Level	N4	N4	N4

Key Differences

1

Certainty Level: かもしれない = 30-50% sure (it's possible). だろう/でしょう = 60-80% sure (it's likely). かもしれない shows more doubt, だろう/でしょう show more confidence.

2

Formality: かもしれない = neutral. だろう = casual/informal. でしょう = polite/formal. かもしれません exists as the polite form of かもしれない.

3

Tag Question Usage: だろう？/でしょう？ at the end of a sentence seeks agreement like 'right?' or 'isn't it?'. かもしれない cannot be used this way.

4

Speaker's Stance: かもしれない = hedging, admitting uncertainty. だろう/でしょう = asserting an expectation or judgment. かもしれない is more humble about knowledge.

5

Question Formation: かもしれない can form genuine questions: かもしれないですか？(Do you think maybe...?). だろうか/でしょうか shows the speaker wondering.

When to Use Which?

Follow this decision guide to choose the right grammar point.

Yes

Use かもしれない

No

Use だろう

No

Yes

Use だろう

No

Use かもしれない

Examples with Explanations

かもしれない

雨が降るかもしれない。

Ame ga furu kamoshirenai.

だろう

明日は雨だろう。

Ashita wa ame darou.

でしょう

明日は雨でしょう。

Ashita wa ame deshou.

かもしれない

彼は来ないかもしれない。

Kare wa konai kamoshirenai.

だろう

彼は来ないだろう。

Kare wa konai darou.

でしょう

この映画、面白いでしょう？

Kono eiga, omoshiroi deshou?

だろう

もう終わっただろう。

Mou owatta darou.

かもしれない

あの人は先生かもしれません。

Ano hito wa sensei kamoshiremasen.

Common Mistakes to Avoid

Mistake #1Using かもしれない when confident

Correction: Use だろう/でしょう when you're fairly sure

かもしれない shows low certainty. If you're 70%+ sure, use だろう/でしょう.

Wrong: 太陽は東から昇るかもしれない。 -- The sun might rise from the east (it definitely does!)

Correct: 太陽は東から昇るだろう。/ 昇る。 -- The sun probably/will rise from the east

Mistake #2Using だろう in polite situations

Correction: Use でしょう in formal/polite contexts

だろう sounds casual and can be rude in formal situations. Switch to でしょう.

Wrong: お客様は何時に来るだろう？(to a colleague about a client) -- When will the client come? (too casual)

Correct: お客様は何時に来るでしょう？ -- When will the client come? (appropriate politeness)

Mistake #3Using かもしれない as a tag question

Correction: Use でしょう？or だろう？ for 'right?' or 'isn't it?'

かもしれない expresses possibility, not seeking agreement. Use でしょう？/だろう？ for confirmation.

Wrong: この料理、おいしいかもしれない？ -- This food might be delicious? (doesn't seek agreement)

Correct: この料理、おいしいでしょう？ -- This food is delicious, isn't it?

Mistake #4Forgetting かもしれません (polite form)

Correction: Use かもしれません in polite situations

かもしれない has a polite form too: かもしれません. Use it in formal contexts.

Wrong: 遅れるかもしれない。(to your boss) -- I might be late (too casual for boss)

Correct: 遅れるかもしれません。 -- I might be late (appropriately polite)

Memory Tips

Tip 1

Certainty Scale

Picture a scale: かもしれない (maybe, shrug) → だろう/でしょう (probably, nod) → はずだ (should be, firm).

Example: 雨かも (shrug) → 雨だろう (nod) → 雨のはずだ (confident)

Tip 2

Polite Pair

Remember: だろう = casual bro talk, でしょう = polite version. Same meaning, different register.

Example: To friend: そうだろう？ / To boss: そうでしょうか？

Tip 3

Question Tag Test

If you want to add 'right?' or 'don't you think?', you need でしょう/だろう, not かもしれない.

Example: いいでしょう？ (Good, right?) vs いいかもしれない (It might be good — no tag)

Practice Exercises

Test your understanding with these practice questions. Click on your answer to see if you are correct.

0 / 6 answered

Q1

あの店は高い___。行ったことがないから分からない。

That store might be expensive. I've never been so I don't know.

Q2

明日の天気は晴れ___。（天気予報）

Tomorrow's weather will probably be sunny. (weather forecast)

Q3

この問題は難しい___？

This problem is difficult, isn't it?

Q4

彼は来ない___。さっき「忙しい」と言っていたから。

He probably won't come. He said he's busy earlier.

Q5

申し訳ございませんが、少々遅れる___。

I'm sorry, but I might be a little late.

Q6

この映画、面白い___？一緒に見た後

This movie is interesting, isn't it? (after watching together)

Frequently Asked Questions

What's the difference between でしょう and だろう?

Can I shorten かもしれない to かも?

How is はずだ different from these?

When do I use でしょうか vs だろうか?

Is だろう masculine?

Summary

Use かもしれない when...

Expresses possibility with uncertainty. The speaker acknowledges something could be true but isn't sure. Often used when the speaker has limited information.

Use だろう when...

Expresses the speaker's conjecture or expectation. Higher certainty than かもしれない. Also used as a tag question seeking agreement. Casual/masculine tone.

Pro Tip: The best way to master the difference is through reading and listening practice. Pay attention to how native speakers use these grammar points in context.