Could you give me an equivalent to these expressions?
Be not to know.
I ought to know.

Examples in sentences:

‘I'm sorry, I called when you were in bed.’ ‘Don't worry—you weren't to know.’
'Are you sure there's no sugar in this coffee?' 'Of course. I ought to know, I made it!'

Ps: It seems that "I ought to know" could be replaces by "I am".

Question

Could you give me an equivalent to these expressions?
Be not to know.
I ought to know.

Examples in sentences:

‘I'm sorry, I called when you were in bed.’ ‘Don't worry—you weren't to know.’
'Are you sure there's no sugar in this coffee?' 'Of course. I ought to know, I made it!'

Ps: It seems that "I ought to know" could be replaces by "I am".

Answer

"You weren't to know" is a phrase used in British English. It is *not* used in American English. An equivalent in American English would be "You had no way of knowing."

"I ought to know" means "I should know [there's no sugar in the coffee] because I'm the one who made the coffee, and I didn't put sugar in it."

NOTE: "should" and "ought to" often refer to obligation. "I ought to make coffee for my wife."

But in your sentence, "should" or "ought to" refers to "reasonable expectation" or "possibility."  I can be expected to know that there is no sugar in the coffee, because I made it."  Here, the probability of the person who made the coffee knowing that it contains no sugar is 100%.

Answer

‘I'm sorry, I called when you were in bed.’ ‘Don't worry—you couldn't have known.’
'Are you sure there's no sugar in this coffee?' 'Of course. I should know, I made it!'

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