That can't be vs That's impossible

When to use each in English, with meaning, register, and examples.

That can't be

Top 2,000 (common)

That's impossible

Top 2,000 (common)
 That can't beThat's impossible
Pronunciation🇬🇧 //ðæt kɑːnt biː//🇺🇸 //ðæt kænt bi//🇬🇧 //ðæts ɪmˈpɒsəbl//🇺🇸 //ðæts ɪmˈpɑsəbl//
MeaningIt is impossible or not true that something is the case.It cannot be done.
ExampleShe got a perfect score on the test? That can't be!When I heard his plan, I thought, 'That's impossible.'
RegisterNeutralNeutral
How commonTop 2,000 (common)Top 2,000 (common)
Collocationsthat can't be true, that can't be serious, that can't be possible, that can't be happeningThat's impossible to believe, That's impossible to achieve, That's impossible to accept
Common mistakesMisuse as a statement of fact rather than opinion., Confuse with 'that cannot be' which sounds more formal., Employ in overly formal contexts where simpler expressions fit better.Using 'that's impossible' too casually in formal discussions., Confusing the expression with 'it's impossible' when addressing multiple situations., Overusing the phrase for minor challenges.
Usage notesUsed to express disbelief or disagreement. Suitable for both spoken and written contexts, though less formal than academic language.Use this phrase to express disbelief or skepticism in a situation. It is suitable for informal and formal situations, but can sound a bit strong depending on tone.

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That can't be
That's impossible

Frequently asked questions: That can't be vs That's impossible

What's the difference between That can't be and That's impossible?

That can't be: It is impossible or not true that something is the case. That's impossible: It cannot be done.

Can you show an example of each?

That can't be: She got a perfect score on the test? That can't be! That's impossible: When I heard his plan, I thought, 'That's impossible.'

Can I use That can't be and That's impossible interchangeably?

Not always. That can't be and That's impossible are related and overlap in some contexts, but they differ in register, how common they are, and usage, so swapping one for another can change the meaning or tone. Check the differences above before substituting.

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