|This article relies largely or entirely upon a single source. (July 2013)|
In sports in Canada and the United States, the phrase games behind or games back (often abbreviated GB), is a common way to reflect the gap between a leading team (said to be that many games ahead or GA) and another team in a sports league, conference, or division. It is the average of the absolute difference in losses between a leading team and the team of interest from the absolute difference in wins between the two teams. The leading team itself is always zero games behind, by definition, and this is typically indicated in tables by a dash ('-') rather than a zero.
GB is calculated using the following formula, in which TeamA is the first-place team, and TeamB is the trailing team:
This formula gives the GB for TeamB. The leading team (TeamA in the formula) is always 0 GB (usually indicated with a dash in standings tables).
For example, if the Cleveland Indians are three games behind the Chicago White Sox for first place, Cleveland would have to win three games, and Chicago would have to lose three, to tie for first. A "games behind" situation changes rapidly when two teams contesting the lead play each other since a zero sum game plays out. In this case, Cleveland would pull even with Chicago in a clean sweep of all three games.
It is often used in professional baseball and basketball, where tie games are not permitted, and to a slightly lesser extent in American football where ties are rare (they officially count as half a win and half a loss, but can be omitted entirely when calculating GB since the "wins minus losses" values for a given team will be the same either way). Usually, in tables of standings in newspapers and magazines kept during the season, teams are ordered by the teams' winning percentages, with the number of games they are behind the division leader supplementing the table. On rare occasions, it is possible (and has occurred) for the team with the second best winning percentage to lead the team with the best winning percentage in terms of games back. This usually occurs during the early portion of a season when teams have played an uneven number of games. For example, if Team A has a record of 23–13 and Team B has a record of 26–15, Team A would be recognized as having a better record by virtue of their .639 win percentage to Team B's .634 percentage. However, in the standings, Team A would still be two and one-half (2.5) games behind Team B, though they would be ordered ahead of Team B.
Also, in some rare situations, also caused in the early season when teams play an unequal number of games, a team with fewer wins could potentially be ahead of a team with more wins. For example, if a team is 26–15, but another team is 25–13, the team with a record of 25–13 is technically one-half game ahead of the 26–15 team, despite having fewer wins on the season.
The "games behind" number is sometimes made in reference to ".500" (even in wins and losses) although in this particular context, the word "behind" is replaced by "under" or "below". In making this calculation, however, the division by two is not done. For example, a team with a record of 19 wins and 20 losses is considered as being "one game under .500", in contrast to being "one-half game behind" a team with a ".500" record of 20 wins and 20 losses.
Major League Baseball
Major League Baseball defines Games Behind as "Games Behind, the average of the differences between the leading team wins and the trailing team wins, and the leading teams losses and the trailing team losses." 
This statistic is now being calculated somewhat differently in the Major League Baseball professional baseball league. Traditionally games behind was calculated with respect to the team with the highest standing in the league (up through the 1968 season), or to the team with the highest standing in the division (1969 season and later).
The statistic got more complicated for the 1994 season Major League Baseball's two leagues split into three divisions each, and added a wild card team to the playoffs. Following the change, it became common for the media to publish an additional set of standings for the wild card race. It included all teams from a league, with the exception of the division leaders, and games behind was calculated with respect to the team with the highest standing in the division.
The statistic got even more complicated in 2012 when Major League Baseball added a second wild card team. Today, games behind is shown in the media as calculated in two different ways. While games behind the team with the highest standing in the division is calculated in the traditional manner, games behind in the wild card race is calculated with respect to the team with second highest standing in the wild card race. Assuming two or more teams are not tied for first place in the wild card, this results in the team leading the wild card race shown as being so many "games ahead" of second place, usually indicated by a plus sign ("+") in the standings. Currently, both the divisional and wild card statistics are called Games Behind or GB in the media. Major League Baseball's official website distinguishes the two by abbreviating the divisional statistic and the wild card statistic as "GB" and "WCGB" respectively.
National Basketball Association
Sometimes, especially nearing the end of the regular season, GB will be given with respect to the #8 position in the conference standings rather than the #1 spot. Since the 8th position is the last qualifier for the playoffs, this stat gives the GB for teams seeking a playoff berth.
- Magic number (sports), number of wins needed to clinch a championship