algorithm used to calculate 5 star ratings

Question

I need to calculate 5-star ratings like the one on Amazon website. I have done enough search to find what is the best algorithm, but I am not able to get a proper answer. For ex

Answer 1

You may want to check this algorithm out: Calculating Average Rating the Right Way using PHP and MySQL - there's no need of saving each "star" (aka rating grade) and its corresponding number of votes and then having to retrieve thousands of rows from the database every time you need to calculate their average. (unless you want to display exactly how many people rated the given item with 1, 2, 3, 4 & 5 stars)