I am new here on StackExchange. I am curious, since I working on something very UX-related. And I know that there do exist different metrics for measuring the outcome of UX. However, how are these mathematically calculated? E.g. are there any equations/formulas that one can use and apply in practice?
I would say no. I consider UX to be more qualitative than quantitative.
Obviously there could be a situation where, say it's an ecommerce portal that has a high drop-off rate and poor conversions. Depending on your company/team setup it could be a product owner, ux practitioner or Analyst actually reviewing the numbers and flagging the need for improvement. Whoever flags it to the UX practitioner, they do some research design and testing and voila! The conversion rate is now greatly improved for that page due to UX but that measurable outcome is not UX.
Now if you're doing UX testing (heuristic evaluations, A/B testing, one-click tests, etc.) you will have some numbers to make decisions with. You may even want to report and show those numbers in a presentation but don't ever, or at least try your best not to, let KPIs tell the story instead of the experience.