Couldn’t care less
Definition 1 of 1
Pro Tip 1/3Emphasizing Disinterest
Stress that you're extremely uninterested or do not have any emotional investment in the situation. 
He's bragging about his new car, but I couldn't care less.
Pro Tip 2/3Misinterpretation Alert
Be aware that 'could care less' is often mistakenly used, but it implies some level of interest. 
Remember, 'couldn't care less' means no interest at all!
Pro Tip 3/3Casual Conversations
This phrase is usually appropriate in informal settings with friends but not in formal situations. 
In a meeting, say 'It's not a concern to me' instead of 'I couldn't care less.'