Some papers (not Kodak) will have a data sheet with the paper that will give
you that information. Generally speaking the rule of thumb is that from 00 to 3.5 will be the same time ; with 4 up needing a 100% increase as the paper speed decreases in half.
The small print also says "must test for personal results". Or something along those lines. Take that to heart.
With some, the times will vary from grade to grade before reaching 3.5
The paper defaults to grade 2 without a filter, however, make a print a grade 2 filter and then one without and they do not look alike.
In our lab we recommend that students increase exposure about 50% when moving up from grade 3.5 to 4 and above as that works better with the paper, developer and water content in our lab.