- That’s so true.
- That’s for sure.
- I agree 100%
- I couldn’t agree with you more.
- That’s exactly what I think. / That’s exactly how I feel.
- (informal) Tell me about it! / You’re telling me!
- (informal) I’ll say!
- I suppose so.
(use this phrase for weak agreement – you agree, but reluctantly)
Note: Avoid the common error of saying “I’m agree” – the correct phrase is “I agree” or “I’m in agreement” – the second one is more formal.