So you want to know what makes a beer a 4 or a 5? Let's break it down.
Starting on 12/3/14 - we have revised how ratings are calculated.
There are 3 types of ratings of Untappd:
Beer Ratings: These are the ratings that you see on the beer page, wish list, etc. These are now calculated at a PUREaverage. They are not longer weighted against other beers. To get a rating, a beer must have 10 or more ratings.
Brewery Ratings: These are the ratings that appear on the brewery page. These ratings are calculated by providing weight to the highest checked in beers, and making their ratings count higher than beers with low rating count. The official formula:
(A*Y)+(B*Z)... / (Y+Z).., where A and B are the pure average of the beer, and Y and Z are the check-in counts for a beer.
Top Beers: These are the beers you see on the "Top Rated" page on the web. These ratings, are still done by our old system (Bayesian Average - http://en.wikipedia.org/wiki/Bayesian_average). You must have 150 ratings to qualify for this list. PLEASE NOTE: These ratings for Top Beers are not shown on a Beer page. The official formula is below:
$avg_num_ratings // Average number of ratings in all beers $avg_rating // Average rating for all beers $this_num_rating // Number of votes for the beer in question $this_rating // Pure Average Rating for the beer in Question $bayesian_rating = ( ($avg_num_ratings * $avg_rating) + ($this_num_rating * this_rating) ) / ($avg_num_ratings + $this_num_rating);
Ratings are still calculated once per day. Every time you make a rating on Untappd - it will be stored, but the average rating is refreshed on a daily basis.
Frequently Asked Questions about Ratings
When your rate beer on a check-in all previous ratings are averaged up and applied to base beer. You can rate as a many times as you want - but you only get 1 rating per beer per user. This cuts down on rating abuse. If you delete a checkin that you rated, that rating will be removed.
You cannot rate a beer a 0. If you do - it's the same as not rating the beer. By not rating a beer, it doesn't count toward it's total. It doesn't mean a 0 rating.
If you have any questions - let us know by opening a discussion at http://untpd.it/newticket.