I believe so

I believe so

An expression of vague affirmation or assent. A: "It's starting to get dark out, should we start heading home?" B: "I believe so." A: "Is Tom coming today?" B: "Yeah, I believe so—I haven't heard otherwise."
See also: believe
Farlex Dictionary of Idioms.
See also:
  • I suppose (so)
  • I suppose so
  • I think so
  • I suspect so
  • I expect so
  • (that) sounds good
  • (that) sounds like a plan
  • word (up)
  • I expect not
  • I suppose not