Since my rating scale is a little tricky, I'll break it down here. My score at the end of a review is a numerical score out of ten, calculated by averaging the scores out of 5 from five different categories: Main Characters, Secondary Characters, Plot, Writing Style and Ending.
For example, a review might look like this:
Main Characters: 3/5
Secondary Characters: 3.5/5
Writing Style: 4/5
I then add together all the scores (here it is 17) and divide it by the total possible (25). This example would create an overall rating of 6.8/10 (17/25=.68). I'm sure there's an easier way to rate these books, but until then...
My stars on Goodreads are based off of these numerical calculations:
0-2 is a 1 star
2-4 is a 2 star
4-6 is a 3 star
6-8 is a 4 star
8-10 is a 5 star
Sometimes I'll "curve" a rating up or down if I feel the score doesn't accurately reflect a rating. For instance, a numerical rating might be a 7.8 but I'll round it up to a 4 star because of the overall effect after reading it or, conversely, I might rate another book down.