(that's) fine with me
I'm amenable to this situation. A: "How do you feel about going to the eight o'clock movie?" B: "Fine with me!" Sure, spaghetti's fine with me—let's start cooking.
(that's) fine with me
and (that's) fine by me; (that's) okay by me; (that's) okay with meThat 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.