That should/ would do it.

Well, they both have their own literal meanings of course, but if you are thinking of the idiomatic use (exclamation), then only 'should' is correct.

"That should do it!" means either "that is enough" (probably its most common use as an exclamation) or its literal meaning "that will probably do it"

"That would do it" doesn't really have an alternate meaning but is definetly different from "That should do it" and is rarely if ever used as an exclamation.

Hope that helps clarify a bit.

should do it means: based on the information given assuming fact or the current circumstance that has already occured, "that" will probably do the job
would means: "that" will do the job if a certain circumstance will be presented at the time or if the information given turns out to be true

Anonymousshould do it means: based on the information given ...

FYI. The last post before yours on this thread was nearly six years ago.

CJ

Actually, even if it's a late entry, it helps a lot. I mean, many people, like me, search for the answers and are too lazy or think it would take too much time to put our their question, so it's easier just to search for some answers that are already here. And it doesn't matter what was the date when they were posted.

Anonymouseven if it's a late entry, it helps a lot.

True. A lot of students feel that way. That's why I labelled it "FYI" in case the poster hadn't noticed the date and was really expecting a response from someone who may have stopped using this forum years ago.