I went to a meeting at our school the other night where they said that they were changing from an unweighted GPA to a weighted GPA. Although our school calculates a class rank based on weighting courses, it's not in a typical GPA format. Actually, it's more accurate because it doesn't use buckets. However, many colleges look at whatever GPA is shown on the transcript and an unweighted GPA based on 4.0 rarely looks good against a weighted GPA based on a maximum of 5. An admissions person from our state university gave an example of how the head of admissions once said that he was "not comfortable" with someone's GPA even though he should have known it was unweighted. I was surprised to learn that many colleges value GPA, but don't bother (probably a money issue) to calculate their own even though they know there is no national standard even for weighting. It's also interesting that some people can make bad holistic decisions.
They said that across the nation, many colleges are ignoring class rank even if it is adjusted for class size. If the class rank is the only thing that reflects the difficulty of the courses taken, it will be ignored and the college may just look at the unweighted GPA. So much for holistic consideration. The admissions person said that one might get rejected in the first cut and never get to any sort of holistic evaluation. And even in the holistic process, your numbers can help or hurt. So the goal is to maximize your numbers to get into the highest holistic academic/EC bucket you can.
One formula is the Academic Index used by Ivy League colleges. Apparently, it dropped its rank portion (dependent on class size) and added in one based on GPA, although it requires recalculating the GPA into a standard form.
There is also this, which gives a spreadsheet calculator.
Although AI was developed for athletes, they calculate it for all students.
The first part is based on your SAT scores, the second part is based on your SAT II scores, and the third part is based on your GPA. The link above talks about a GPA table supplied to the eight universities, but it doesn't explain how the GPA is calculated. It appears to use a weighted scale where the top score is 4.3. I haven't found out how this number is calculated. The spreadsheet then proceeds to choose the higher score associated with each of the two GPA numbers. It's always struck me that the SAT scores make up two-thirds of this index. Colleges might include a fudge factor if they know something about a high school, but no option for that shows up in the example spreadsheet.
The problem with rank is that you can't correct for it based on whether it uses weighted or unweighted GPA. Recalculating the GPA is good because it isolates the variable of grades. Some colleges are calculating unweighted GPAs using just the core academic courses. Then they can provide a factor for how much you challenged yourself given what your high school has to offer. Then they can correct again if they know something about the difficulty of your high school. At our meeting, they repeated the nugget that "it's best to get A's in AP classes." My nuanced view is that it's best to have the highest unweighted GPA while still looking like you are challenging yourself. Colleges want 'A' students. It's better to have them think you could have challenged yourself more rather than to do so, but slip.