Fielding Percentage #1 
(Attempts  Errors) divided by (Attempts)
The fielding percentage, or fielding average, defensive statistic is the most common rating system being used in baseball today. It is meant to measure the success rate of fielding opportunities by each player. The official scorer for each game plays a role in this statistic by determining if the hit ball would have required an ordinary amount of effort to turn the play (thereby charging an error to the fielder if they did not turn the play) or an extraordinary amount of effort to turn the play (which does not result in an error charged to the fielder). The downfall to this statistic is that it almost rewards fielders who choose not to attempt a difficult play, thereby avoiding the error, to those that try to turn every hit ball into a possible out. This is the version most often seen in youth, high school and college statistics. 
Fielding Percentage #2 
(Putouts + Assists) divided by (Putouts + Assists + Errors)
This version of fielding percentage is calculated differently but both fall within a few percentage points of each other by year end. Errors also play the same critical part in this method. The official scorer for each game is the determining factor in an error or a hit. Again, slacking off seems to favor the fielder. This is the version most often seen in pro ball. 
Games Won Percentage 
Games Won Percentage = Games Won divided by (Games Won + Games Lost)
The win percentage is the bottom line statistic. It is meant to measure the success of the team; the counterpart is Games Lost Percentage. 
Games Lost Percentage 
Games Lost Percentage = Games Lost divided by (Games Won + Games Lost)
The win percentage is the bottom line statistic. It is meant to measure the success (or lack of it) of the team; the counterpart is Games Won Percentage. 
Range Factor [RF] 
(Putouts + Assists) x 9 divided by Defensive Innings Played
Range Factor simply stated is the number of plays MADE per game at the fielding position. It is better than Fielding Percentage in several respects in that it can be calculated for almost any player, in any league, as far back as statistics go, and it takes into account the fielder's own ability to get to a batted ball. That in turn rewards effort from the more gifted players at each position. Positions can only be successfully compared to the same position on the field when using this statistic and early in the season numbers are often skewed as players chances are not yet normalized. 
Fielding Runs [FR] 
Fielding Runs is a common term for any statistical treatment of fielding that converts a fielder's performance to runs. Total Baseball uses the most common approach and most easily understood version. Their approach involves weighting the number of putouts, assists, and double plays made by each fielder, and comparing those totals to positional norms of other fielders to arrive at a figure above or below average. Some teams include errors, effort, and who is hitting into the equation. Each extra out made, or hit allowed, is worth X runs which leads to the FR figure. Career figures are considered better indicators than individual seasons as normalization is required for better overall averaging of each fielder's statistical performance; however since teams often calculate differently and few players play for only one team during a career, that has become virtually impossible to calculate. There is really no formal formula for this. 
Zone Rating [ZR] 
STATS, Inc. developed their own defensive rating system to also track locations of EVERY hit ball for EVERY game played  similar to the above Defensive Average statistic. The Zone Rating system is different because the area of responsibility, or zone, for each fielder is considered a "playable" area and does not account for balls hit into "Bermuda Triangles", "No Mans Land" or other impossible to field balls. A fielder that turns a double play is credited with 2 outs in the ZR system as their play on the ball actually resulted in both outs versus Defensive Average which only credits the 1 out. STATS, Inc. books area available at every bookstore and their work is updated on a yearly basis for player comparisons. The information and formulae are proprietary but interesting nonetheless. 
Defensive Average or [DA] 
The Baseball Workshop & Project Scoresheet has been methodically placing the location of EVERY hit ball for EVERY game during the last several years. A Defensive Average, or DA, is the rate at which fielders in their respective "zone" turn hit balls into an out. The zone, or area of responsibility, spans the entire field and no section of the playable field is considered beyond the reach of a fielder. The Defensive Average statistics is nice because it is the counterpart to a fielder's Batting Average Against in that it specifically measures times reached per opportunity. However, it is more subject to conjecture of what is in a territory and is playable. The two standard formulae are the same as Fielding Percentage.
