Range Factor is determined by dividing the sum of a fielder's putouts and assists by his total number of defensive games played.
More recently, Range Factor per nine innings has evolved as the more prevalent statistic because it addresses the discrepancies between a player who plays one inning in a given game and a player who plays the full game.
There are flaws with Range Factor -- namely that the circumstances for fielders can vary greatly. With ground-ball pitchers on the mound, for example, an infielder is bound to receive more opportunities to boost his Range Factor. The advent of defensive shifts has affected Range Factor further. For instance, a third baseman who is used frequently in shifts will likely have a higher Range Factor than one who isn't -- even though defensive positioning is generally determined by the manager or bench coach.
Still, Range Factor answers a pivotal question that went long unanswered when fielding percentage was used as the primary evaluative defensive metric: How many plays can a given fielder make? Or, put more simply, how much range does a fielder have?
Noted sabermetrician Bill James coined Range Factor as a means of assessing a player's defensive capabilities outside the realm of his fielding percentage. As many now agree, fielding percentage often produces a deeply flawed number, but at the time of James' invention of Range Factor, fielding percentage was the primary evaluative metric for defenders.
Watch: Scooter Gennett backpedals to make a catch, boosting his Range Factor.
In A Call
"range rating," "range average"