GPA data across majors
This data is available for the United States as part of the NCES Baccalaureate and Beyond Longitudinal Study (B&amp;B). You can create a free account, then run some basic data analysis on their data using their PowerStats tool. (You could definitely use it to compute what "percentile would you be in if you had x GPA in y major" - I just tried it for myself. I was apparently a 95.1st percentile student as an undergrad :))

Here's a table I just made there of 10th, 25th, 50th, 75th, and 90th percentile GPA by major: