Does that expression mean "I'm totally sure" or "I'm almost sure"? I always thought the first option was correct, but once I saw in a series episode a character who said that, and his interlocutor expressed skepticism about it (something like "Are you sure or pretty sure?"). Does that depend on context, or does it always mean the same?
Word Usage – What Does ‘I’m Pretty Sure’ Mean?
meaning-in-contextword-usage
Best Answer
We can't assign a percentage of certainty to it, but it isn't close to 100%. Perhaps 60-85% certain is close to what it means for most native speakers. The more emphatic the statement (stress and pitch and volume are involved, because this is primarily spoken English, but in written English it might be underlined or in bold font or in capital letters for emphasis), the more certain the speaker/writer is. I'm quite sure probably means about 90-100% certain, however.