There's the relative number line etc, but I've never actually encountered a situation where I felt the need to make a jump to a line number on the screen and didn't do it with basic vim motions instead. Every time I'm going to a specific line number, it's because I'm following an error message that references a file and line number.

Moving 15 lines up is a basic vim motion

I can't easily do such mental arithmetic quickly enough for it to be faster than just estimating the number of lines and correcting.

I once tried to solve this by using relative numbers and it didn't help much. I just turned the number line off.