1
general::
Phrase(s): (That’s) fine with me. [and] (That’s) fine by me.; (That’s) okay by me.; (That’s) okay with me.
That is agreeable as far as I am concerned. (The expressions with by are colloquial.) • Sue: I’m giving away your old coat. Bob: That’s fine with me. • Sally: Can I take twenty dollars out of your wallet? Fred: That’s okay by me—if you can find it, of course.
McGrawhill's American Idioms And Phrasal Verbs