Update 2: 1UP Vice President Simon Cox has contacted Joystiq to let us know there are some bugs associated with the current roll out of the conversion formula. Specifically, Cox said the full range of grades (including those marked with a dash in the chart) should have been used in the conversion, and will be when the bug is fixed by the end of the week We'll update the chart and this post when that happens.
Update: Since there appears to be some confusion in the comments, a dash in the "Number" column on the chart means that there's no number score that corresponds to that letter grade.
As part of a planned reorganization, 1UP today switched from its well-known 0-10 review scale to a school-style letter grading scheme. The changeover included a conversion of all existing review scores on the site from numbers to letters, but, as Editorial Director Dan Hsu told N'gai Croal, the site will not be publishing a simple conversion scale to figure out which old number ratings apply to which new letter grades, Hsu says they're keeping the scale close to their chest "because we want our readers to go with our new scoring system and not be constantly translating the new letters back to our old scores."
Where's the fun in that? We compared some old numerical ratings to the new letter grades for ourselves and created the handy (if a bit ugly) conversion chart on the right. Read on for way too much analysis of the score conversion and what it means for evaluating 1UP review scores going forward.