Make the grading numbers "round"
I teach math. I was perplexed that students couldn't compute the percentage that they scored (after all, it is a math class). So, I made everything a round number. Every homework assignment is worth 10 points. When I had 19 sections of homework (this matched the number of sections in the textbook), I threw in one "freebie" so I would have 20*10 = 200 points. It makes it easier for the students to track (and me too).
When I was a grader in graduate school, one of the professors I helped suggested that since all the questions in a problem set were equally difficult, then each question should be worth 10 points. To get a percentage, I would add up all the accumulated points and divide by the maximum number of points; I write both the fraction and percentage at the top of the first page of the graded assignment. Whilst in grading mode, this is ideal for me as I like to give partial credit.
To keep track, I normally rely on Engrade's online gradebook platform automatic calculations. Nonetheless, I prefer to forecast scores using my own records on an Excel spreadsheet. It's quick to setup a template and import or insert grades manually from my gradebook.
