「I don’t know」の丁寧で自然な言い換え方｜英語での断り方をマスターしよう
Sometimes in English, what you say is less important than how you say it.
Saying “I don’t know” is simple, but depending on the situation, it can sound too direct, too casual, or even a little rude.
In this post, we’ll look at natural, polite, and more expressive ways to say “I don’t know.” We’ll also explain when to use them.
1. The Basics
I don’t know - neutral, standard
“I don’t know where he went.”
This is fine in most situations. However, if your voice sounds too flat or cold, it can feel a little unfriendly.
I’m not sure - softer, more polite
“I’m not sure where he went.”
This is a very common way to say “I don’t know” politely, especially in formal or customer service situations.
2. Adding Softening Language
To sound more polite or less direct, you can add extra phrases:
I’m afraid I don’t know - polite and formal
“I’m afraid I don’t know where he went.”
This phrase is often used in professional or service roles (like in a restaurant/shop). It’s polite, apologetic (feeling of ‘sorry’), and soft.
I’m not quite sure - a gentle way to say you don’t know
“I’m not quite sure where he went”
The word “quite” softens the phrase and makes it sound less strong.
To be honest, I’m not sure - adds honesty and a softer tone
“To be honest, I’m not sure where he went.”
This phrase is often used when you want to be clear and honest, but also polite. It sounds friendly and natural in conversation.
3. Casual, Everyday Phrases
No idea - casual and short
“Where’s my pen?”
“No idea!”
This is often used with friends, but can sound too casual or rude in formal situations.
I’m not sure, sorry - common in everyday speech
“I’m not sure, sorry – maybe ask the manager.”
Adding “sorry” softens the sentence and shows you want to help.
Beats me - very casual and idiomatic
“Why did they cancel the class?”
“Beats me!”
This is informal and shouldn’t be used in professional situations.
4. When You Want to Guess or Offer Help
Sometimes, you don’t know the answer, but you want to help or make a guess:
I think it might be… - offering a possible answer
“I think it might be around 3 o’clock.”
I’m not sure, but maybe… - polite and helpful
“I’m not sure, but maybe it’s in the drawer?”
I don’t know off the top of my head - you don’t know right now, but you might know it later
“I don’t know off the top of my head, but I can check.”
5. Cultural Note: Tone Matters
In English, especially British English, how you say something is very important.
A simple “I don’t know” with a flat or cold voice can sound rude or uninterested.
To sound more natural and friendly:
Smile (if in person)
Use softeners like “I’m not sure,” “to be honest,” or “I’m afraid I don’t know”
Offer help, if possible: “I’m not sure, but I can find out”
This shows you care, even if you don’t have the answer.
Quick Practice
Choose the most natural or polite response:
A customer asks where the toilet is (you don’t know).
A friend asks where your bag is (you don’t know).
Your manager asks when the report is due (you forgot).
A stranger asks for directions (you’re unsure).
Your classmate asks a difficult grammar question (you don’t know the answer).
Possible Answers
I’m afraid I don’t know.
No idea!
To be honest, I’m not quite sure.
I think it might be that way, but I’m not sure.
I don’t know off the top of my head.