Hey guys, from what I have observed, I doubt that there is one unified conversion that determines exactly particular selection ranks in terms of GPA and that is applicable to all universities. It would be reasonable to suggest that each university's approach to converting a student's GPA to a selection rank may be different. For instance, the University of Queensland's conversion for students who studied 1+ year full-time (or part-time equivalent) treats a GPA of 4.8 as being equivalent to a selection rank of approximately 95.5. This is slightly higher than that of Griffith University, where a GPA of 4.8 converts to a selection rank of approximately 95.4.
There was also a proposed GPA to selection rank conversion (about 3 years ago I believe), which appears to be from UAC. Under that conversion, a GPA of 4.8 converts to a selection rank of 86.95 if the student has completed 1 or more years, but less than 3 years, of full-time study (or part-time equivalent) and 91.15 if the student has completed 3+ years of full-time study (or part-time equivalent). This was included in a document from USyd, which at the very least could suggest that USyd may have considered this particular conversion from UAC.
Liamk858, this means that, not only could a GPA of 4.8 be treated as different selection rank values depending on the university that you are interested in attending, but your progress in terms of your current degree (i.e. how much of your current degree you have completed) is also an element that you should remain aware of, where greater progress is associated with a more generous conversion. From this information, you are likely on track in terms of maximising your chances of receiving an offer to your chosen degree, although I would recommend doing your utmost to improve your GPA to 5 and, if possible, 5.3.
I hope this helps!