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

According to your question your solution will be like this.

Sum of (Rate*TotalRatingOfThatRate)/ TotalNumberOfReviews

((5*252)+(4*124)+(3*40)+(2*29)+(1*33)) / (252+124+40+29+33)

output will be 4.1