Baseball Glossary › Range Factor
Range Factor (RF)
Range factor (RF) measures how many plays a fielder makes, dividing putouts plus assists by games played in the field. The more common modern version, range factor per nine innings, divides by innings instead and multiplies by nine. Bill James created it to capture range, something fielding percentage ignores.
Formula
Worked example (illustrative numbers): a second baseman has 250 putouts and 380 assists in 1,260 innings in the field.
PO + A = 630
RF/9 = 9 x 630 / 1,260 = 4.50 plays per nine innings
What to Know
Range factor answers a different question than fielding percentage. Fielding percentage asks how cleanly a player handles the balls he reaches; range factor asks how many plays he makes at all.
It has blind spots. A staff of ground-ball pitchers sends more balls to the infield, and defensive positioning decided by the manager can raise or lower a fielder's opportunities. Range factor also uses the same putouts and assists every scorer records, without asking how hard each play was. Statcast's Outs Above Average addresses that by grading each play's difficulty.
Frequently Asked Questions
What is range factor in baseball?
Range factor is a fielding stat that divides a player's putouts plus assists by the games he played in the field. It estimates how many plays he makes per game, which is a rough measure of his range.
How do you calculate range factor?
Add putouts and assists and divide by defensive games. For range factor per nine innings, multiply putouts plus assists by 9 and divide by innings played. For example, 630 plays in 1,260 innings is 4.50 per nine.
Who invented range factor?
Range factor was created by the sabermetrician Bill James as a way to judge defenders on how many plays they make, rather than only on how many errors they avoid.
Why is range factor per nine innings used more often?
Because a game played can mean one inning or nine. Dividing by innings rather than games removes that distortion, so a late-inning defensive replacement is not compared on the same footing as a full-time starter.
What is the difference between range factor and fielding percentage?
Fielding percentage measures how often a fielder avoids errors on the plays he handles. Range factor measures how many plays he makes per game. A fielder can rate well on one and poorly on the other.
What are the weaknesses of range factor?
It depends on the pitching staff and on positioning. Ground-ball pitchers create more chances for infielders, and shifts or positioning decisions change who gets the ball. It also treats easy and difficult plays the same.
Related Terms
Sources
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