“How do I say ‘I’m surprised’?”
Extremely natural for both positive and negative surprises when an outcome was unexpected.
没想到
I didn’t expect that / surprisingly.
Did not think of / expect.
I didn’t expect that / surprisingly.
WHEN IT FITS
Chinese often prefers to describe surprise through the failed expectation (没想到 — “didn’t see that coming”) rather than by naming the emotion. 我很惊讶 is grammatical but more formal and self-conscious; in everyday speech, 没想到 carries both the surprise and the reason in one natural package. For dramatic contrast, 居然 (“actually / contrary to all expectation”) sits mid-sentence and highlights just how unlikely the outcome was.
HOW PEOPLE ACTUALLY SAY IT
没想到你也来了。
I didn’t expect you to come too.
Unexpected appearance我真没想到结果会这么好。
I really didn’t expect the result to be this good.
Positive surpriseCHOOSE BY SITUATION
居然
Unexpectedly / actually.
You want to highlight how contrary the result was to expectation