You want to maximize the "good" you do in the world. What definition of "good" do you use for this? What definition of moral correctness do you use, and wouldn't it get sufficiently Goodharted if you try, with numbers and probabilities and whatnot, to maximize it?
(I'd caution against truly maximising.)
Ben Todd's 80K article What is social impact? A definition is a pretty decent start:
And their more rigorous definition:
The rest of the article elaborates on what they mean by all the terms in their rigorous definition.
80K also note that this doesn't just reduce to utilitarianism: