What is Wins Above Replacement (WAR) in baseball?

With the new MLB season around the corner, we wanted to take this time to break down one of baseball’s most complicated statistics: Wins Above Replacement (WAR).

In simple terms, WAR is a statistic used to measure a player in all areas of the game by determining his worth against a replacement player in the same position.

The statistic has become commonplace in modern MLB discourse as it relates to which players are having the biggest impact on their team winning games. It has even been used as a factor in determining league awards, such as MVP and Cy Young.

But what is exactly is WAR?

Continue reading for a breakdown of what the statistic means, how it is calculated, its origins, and MLB all-time and single season leaders in the statistic.

What is Wins Above Replacement (WAR) and how is it calculated?

Wins Above Replacement, or WAR, is a sabermetric stat in baseball that measures an individual player's value to their team.

A player's WAR is equal the number of wins their team added with that player in the lineup, as opposed to their replacement.

The statistic measures everything a player does in a game - hitting, baserunning, fielding, pitching - as well as factors such as the ballpark, position(s) played, the value of their "replacement" or back-up, and more. Bottom line, it is a very complex statistic.

It is so complex that there is no one formula adopted by all, rather different variations used by different outlets, notably FanGraphs and Baseball Reference, two of the most reliable platforms for baseball statistics.

See below for the different formulas used to calculate WAR for position players (non-pitchers):

FanGraphs WAR (fWAR) = (Batting runs + Base Running runs + Fielding runs + Positional Adjustment + League Adjustment + Replacement Runs) / (Runs per win)

Baseball Reference WAR (bWAR) = (Batting Runs + Base Running runs +/- Runs from GIDP + Fielding Runs + Positional Adjustment Runs + Replacement Level Runs) / (Runs per win)

The MLB provides the below general formula for WAR on the league website:

The number of runs above average a player is worth in his batting, baserunning, and fielding plus adjustment for position plus adjustment for league plus the number of runs provided by a replacement-level player divided by Runs Per Win.

Calculating WAR for pitchers is even more complex, with formulas even more complex than the above. Per the MLB, the statistic can be calculated using RA9 (runs allowed per 9 innings, used by Baseball Reference) or FIP (fielding independent pitching, used by FanGraphs).

RA9 accounts for the quality of defense and fielding behind the pitcher, while FIP does not. The MLB's official website says that the two calculations for pitcher WAR also take into account league (AL or NL), ballpark, league averages and innings pitched.

You might be wondering, how is WAR a reliable statistic when there is more than one formula for it?

While the two methods don't line up to the exact decimal point, both calculations are considered reliable in determining a player's value to their team.

Origins of Wins Above Replacement (WAR) in baseball

The concept of WAR first became popular in the 1980’s due to the work of baseball writer, historian and statistician Bill James, who pioneered the idea of evaluating players beyond traditional stats, a concept known as sabermetrics.

Later in the 1990s, Keith Woolner introduced Value Over Replacement Player (VORP), a statistic used to measure a player's value compared to their replacement. Throughout the 2000s, the calculations for such measurements were enhanced, including the addition of fielding values, and the overall "value" of a player was translated to team wins.

In the modern day, the formulas have been fine tuned by prominent outlets Baseball Reference and FanGraphs and are widely accepted in baseball circles, including in MLB front offices and clubhouses when it comes to player evaluation.

MLB Career Wins Above Replacement (WAR) Leaders

per Baseball Reference

Player	WAR
Babe Ruth	182.6
Walter Johnson	166.9
Cy Young	163.6
Barry Bonds	162.8
WIllie Mays	156.2
Ty Cobb	151.5
Henry Aaron	143.1
Roger Clemens	139.2
Tris Speaker	134.9
Honus Wagner	131.0

MLB Single-Season Wins Above Replacement (WAR) Leaders

per Baseball Reference

Player	Year	WAR
Tim Keefe	1883	20.2
Old Hoss Radbourn	1884	19.4
Pud Glavin	1884	18.4
Jim Devlin	1876	18.3
Guy Hecker	1884	17.8
Walter Johnson	1913	16.6
Charlie Buffinton	1884	16.3
John Clarkson	1889	16.2
Silver King	1888	16.0
Walter Johnson	1912	15.4

MLB Active Wins Above Replacement (WAR) Leaders

per Baseball Reference

Player	WAR
Mike Trout	86.2
Justin Verlander	80.5
Clayton Kershaw	79.4
Max Scherzer	75.4
Mookie Betts	69.6
Paul Goldschmidt	62.8
Freddie Freeman	60.7
Manny Machado	57.8
Nolan Arenado	56.7
Chris Sale	53.4

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