From the Oxford Advanced Learner's Dictionary:
would imagine, say, think, etc. (that)… used to give opinions that you
are not certain aboutI would imagine the job will take about two days.
I'd say he was about fifty.
Does it means you think so but you are not so sure?
Is it popular in everyday conversation?
Best Answer
The dictionary you quote is perfectly accurate; "I would think", etc., is used in situations where you are expressing an opinion without being too sure about it. The difference between these two sentences is one of nuance:
The first suggests that you have some grounds for your opinion, and the second that you're more or less guessing. See this earlier question for a further discussion.
It should be noted that you would think doesn't mean the same thing at all. If I say:
what I'm actually saying is that the bank has not figured out a secure way to handle fund transfers, and that this is unexpected. Unlike I would think, which is in the nature of a guess, you would think states something contrary to fact.