No, not quite like that... It's like: I'm not completely sure, but that is my opinion. She must be about 40. Yeah, I'd say so - something like that. It looks like they might have to cancel the Tokyo Olympics. I'd say so... a lot of people seem to be against it.

I agree with Charlie. "I would say so" expresses agreement, but not strong agreement. It is less strong than saying "yes". It's like you're leaning "yes" but don't want to come out and say it. But as Ian says, the tone is important (and so is the context), and like many expressions, "I would say so" can be used in different ways.

Oi Grazi, tudo bom? Só um comentário: Em inglês não dizemos "I have a doubt" nesse caso e sim "I have a question". A palavra "doubt" é usado no sentido de duvidar de pessoas/comportamentos/intensões. Quando temos questões ou dúvidas em relação à assuntos/matérias/notícias, etc , usamos "question" Bons estudos o/

It depends on the speaking tone. If the tone is normal / neutral, than the meaning is "probably" or "I think this is correct." If the tone is dramatic or extreme, then it the meaning is strong agreement. For example: "Do you think your futbol team can win the match on Saturday?" "I would say so." (normal tone) "It was a bad idea to get drunk the night before a big test." "I would say so!" (dramatic tone)

The response "I would say so" is technically correct but sounds very strange. I would avoid saying that altogether and just use "yes" or "sure".