How to convert UK score to GPA?

Some programs ask applicants not to convert their GPA to the American scale, but report their GPA in the original scale and explain what the scale was if needed. You can find some info on GPA conversions here: https://aringo.com/gpa-conversions/

Before you start converting you let me save you a lot of effort and tell you that you don’t need to do it.
Since you haven’t mentioned which business school you’re applying to, I can’t tell you for sure whether you would need it or not, but most business schools do not ask for a GPA conversion done by a student. Any business school, whether in the US or the UK, will ask for your complete transcript from your previous course.
They can use this transcript to do the conversions themselves through software they trust and sometimes even pay a small fortune for. Or they could simply look at your performance in certain courses to ensure that you’ll be able to handle the rigor of the MBA program.
London Business School’s statement about the application requirements proves my point, “A transcript of grades from each university you have attended (if you are made an offer). Transcripts also require a certified translation into English.”
So, before you invest too much time and energy in trying to convert your GPA, please check your school’s website under the application requirements or the FAQs section, and make sure your school requires a converted GPA.