From Sega Retro
Rating systems from magazines use only the final percentage score given by a publication, even if the magazine ranks individual components of a game such as music or graphics.
A-F ranking systems
In order to calculate reviews which use A-F rankings, we have adopted a numerical conversion chart keeping in line with those used on aggregate sites such as Metacritic and Mobygames. This allows for simple calculation of a game's review on a 100-point scale.
Aktueller Software Markt
Reception scores for Aktueller Software Markt are calculated by taking the mean score from the five rankings the magazine gives: Grafik, Sound, Spielablauf, Motivation, and Preis/Leistung. This average is then multiplied by 10 to calculate the final score.
French magazine CD Consoles initially used a system of "stars" divided into five sections; "Créativité", "Jouabilité", "Graphismes", "Son" and "Potentiel". Each section could be awarded a maximum of five stars, giving a possible 25 stars in total. The given score (in stars) should be multiplied by four to get the final score.
Later magazines opted for a pseudo-percentage system instead.
Electronic Gaming Monthly
The very first issue of Electronic Gaming Monthly graded games as "near hit", "hit" and "direct hit". Assuming there was an unused "miss" score, these are taken to mean 50, 75 and 100 percent respectively.
Reception scores for subsequent issues of Electronic Gaming Monthly are calculated by taking the average of the three or four (depending on the era) review scores given by each reviewer and determining the mean average. From there, the decimal is carried from a 10 point system to a 100 point system. After April 2008, review scores switched to an A-F ranking system and should be calculated by the previously mentioned chart, and again, the mean average should be derived for the final score.
Reception scores for GamePro are calculated by taking the four 0-5 ranked ratings (Graphics, Sound, Control and Fun Factor), deriving the mean average of the numbers, and multiplying that number by 20. Please note that this method of calculation is different than most websites, which base their meta-ranking off the "Fun Factor" score exclusively.
Reception scores for Electronic Gaming Monthly are calculated by taking the average of the four review scores given by each reviewer and determining the mean average. From there, the decimal is carried from a 10 point system to a 100 point system.