Game Score is a metric invented by Bill James that attempts to quantify a starting pitcher’s performance in one number. Here’s how it’s calculated:
Start with 50 points.
Add one point for each out recorded, so three points for every complete inning pitched.
Add two points for each inning completed after the fourth.
Add one point for each strikeout.
Subtract two points for each hit allowed.
Subtract four points for each earned run allowed.
Subtract two points for each unearned run allowed.
Subtract one point for each walk.An average major-league start will post about 50 points.