Wins Above Replacement (WAR) is a player-value metric, an attempt to translate a player's total contribution on the field into a single number, while allowing for comparison across positions, leagues, eras, etc.
Since we added our WAR metric to baseball-reference in 2010, we've seen its use expand into many new areas and its popularity catch on in the media and general population. But there have also been a lot of questions about how it's calculated and whether it has validity.
On baseball-reference.com, we've put together a comprehensive informational guide to WAR, including a very detailed explanation of the calculations used in WAR and an explainer about how our approach differs from some of the other popular WAR or WAR-like metrics.
If you're interested in learning about how to use WAR, the concept of replacement-level players, the changes we've made to our WAR calculations over the years, etc., please go to this link: https://www.baseball-reference.com/about/war_explained.shtml
For a comparison of the different WAR frameworks (i.e. Fangraphs, Baseball Prospectus, etc.), please go to this link: https://www.baseball-reference.com/about/war_explained_comparison.shtml
To obtain a daily downloadable archive of our WAR data going back to 2013, please click here: https://www.baseball-reference.com/data/