How do you know when you’ve fallen out of love with an ex?

When you stop wondering if you still are in love with him/her.

If seeing them evokes no emotional response at all, you're done.
If realizing that you no longer have to live your life to suit them, brings you nothing but a sense of relief, you're done.

When you are kind of skeeved out by the fact that you were ever dating them....

When you don't miss talking to them or seeing them anymore. You hardly think of them

You feel indifferent toward them.

You two are EXES