There was an article in the Stanford alumni magazine a number of years ago that discussed admissions. They estimated that 80% of the applicants to Stanford are academically fully qualified to attend and do well.
I have heard estimates that 85% of applicants to MIT are qualified to attend. One issue here is that MIT has a reputation of being academically challenging, which leads to some self-selection of candidates. IMHO this reputation is well earned.
For Stanford, and the Ivy League schools, and most other universities, these stats are somewhat skewed in that they include recruited athletes, who are of course way more likely to be accepted.
If we look at the Stanford numbers, let’s assume that the acceptance rate is 4%, and that 80% of applicants are qualified. This would mean that the acceptance rate only considering qualified applicants is 5%. However, then you need to subtract the number of recruited applicants that were accepted. Assuming that you are academically qualified but you are not a recruited athlete, this might put your chances back to about 4%, or maybe less.
There are a few applicants for whom the stats may be adjusted. As one example, I knew someone as an undergraduate at MIT who had won a significant international competition and whose father was the head of state of a medium sized country. I expect that her chances were probably better than the average applicant. I have occasionally heard of young Nobel prize winner or the children of famous people (such as presidents) attending famous universities (eg Chelsea Clinton attended and graduated from Stanford). Again, if none of this applies to you then this might reduce your chances.
However, I do not think that it is possible to give a precise number for your chances of acceptance to a highly ranked university. There are a lot of universities. Some students do get to attend the famous ones. You apply and see what happens.
Also apply to safeties.