Reaching base is the most important thing a batter can do in baseball. Getting on base more often equates to scoring more runs and ultimately winning more games. But, some methods of reaching base are more effective than others in scoring runs, which is what wOBA measures.
So, what is wOBA in baseball?
Weighted on-base average, or wOBA, measures how often a player reaches base and how they reach base. Hits that produce more runs, like home runs, have the highest weight in calculating wOBA. Hit by pitches and walks have the lowest weight since they are less likely to score runs as a result.
This article explains what wOBA is and how it compares to other stats like OBA and OPS. It also explains what a good and bad wOBA is and covers the all-time wOBA leaders. Lastly, we’ll go into detail on xwOBA and decide if wOBA is a good stat.
What Is wOBA in Baseball?
wOBA is a stat in baseball used to measure how often a player reaches base and how likely they are to score runs as a result of reaching base.
Here is the MLB’s definition of wOBA:
wOBA is a version of on-base percentage that accounts for how a player reached base — instead of simply considering whether a player reached base. The value for each method of reaching base is determined by how much that event is worth in relation to projected runs scored (example: a double is worth more than a single).
For instance: In 2014, a home run was worth 2.101 times on base, while a walk was worth 0.69 times on base. So a player who went 1-for-4 with a home run and a walk would have a wOBA of .558 — (2.101 + 0.69 / 5 PAs).
As you can see in the formula above, home runs are weighted significantly higher than walks in the wOBA formula. The other ways of getting on base (hit by pitch, singles, doubles, and triples) all weigh between a walk and a home run.
So, wOBA gives more weight to hits that give you multiple bases and are more likely to produce runs. The more bases you get on hits, the higher your wOBA.
What Is OBA in Baseball?
On-base average, also called OBA or on-base percentage, is similar to wOBA, but every method of reaching base has the same value in calculating the stat. So a home run, a single, and a walk count the same.
Here is the MLB’s official definition of OBA:
OBP refers to how frequently a batter reaches base per plate appearance. Times on base include hits, walks and hit-by-pitches, but do not include errors, times reached on a fielder’s choice or a dropped third strike. (Separately, sacrifice bunts are removed from the equation entirely, because it is rarely a hitter’s decision to sacrifice himself, but rather a manager’s choice as part of an in-game strategy.)
A hitter’s goal is to avoid making an out, and on-base percentage shows which hitters have accomplished that task the best.
On-base percentage can also be applied as an evaluative tool for pitchers, although this is done less frequently. In such cases, it is referred to as on-base against.
OBA and wOBA both determine how often a player reaches base. But with OBA, it doesn’t matter if you have a walk, a single, or a home run. All methods of getting on base give you the same OBA.
What Does wOBA Measure?
wOBA measures how good a player is offensively. The higher the wOBA, the better a player is at reaching base and producing runs as a result of reaching base.
The more multi-base hits a player has, the higher their wOBA will be. The reason is that multi-base hits (doubles, triples, and home runs) have the highest weight when calculating wOBA.
So, a higher wOBA means a player is getting more home runs, triples, and doubles and likely produces more runs for each hit.
And, an average wOBA doesn’t mean a player is not as good offensively, but that they are hitting more singles or walking more than they are getting multi-base hits.
A low wOBA means the player is either not reaching base as often as they should or getting a lot of walks to get them on base. With many walks, they are still getting on base, but them getting on base is not producing runs. Since walks are weighted lowest in the wOBA formula, more walks mean a lower wOBA.
You may wonder why walks and hit by pitches have a lower weight than singles when all of them only get the batter one base. Well, wOBA also measures how effective each way of reaching base is at scoring runs.
While all three of these only get the batter to first base, other players can still score on each one. For a run to score on a walk or hit by pitch, the bases have to be loaded, and the runner at third will score. But, on a single, up to three runs can score if the bases are loaded since the runners aren’t limited to only one base.
wOBA Formula
The formula for calculating wOBA is always the same, but some of the numbers within the equation, called factors, change each year.
Here is the MLB’s official formula for wOBA:
Where “factor” indicates the adjusted run expectancy of a batting event in the context of the season as a whole: (unintentional BB factor x unintentional BB + HBP factor x HBP + 1B factor x 1B + 2B factor x 2B + 3B factor x 3B + HR factor x HR)/(AB + unintentional BB + SF + HBP).
The “factor” in the MLB’s formula above changes every year based on the expected number of runs for each event compared to an out. Home runs have the highest factor since they produce the highest number of runs for each home run. Walks have the lowest factor since they have the lowest number of runs as a result of each walk.
First, here’s the general wOBA formula. Each F stands for the factor for the specific scoring method it’s being multiplied by.
wOBA = (F * Non-intentional Walks + F * Hit by Pitch + F * Singles + F * Doubles + F * Triples + F * Home Runs) / (At Bats + Walks + Intentional Walks + Sacrifice Flies + Hit by Pitch)
Now, let’s look at the wOBA formula for the 2021 season, with each specific factor for getting on base. Below are the factors for each method:
- Non-intentional Walks = 0.692
- Hit by Pitch = 0.722
- Singles = 0.879
- Doubles = 1.242
- Triples = 1.568
Home Runs = 2.007
2021 wOBA = (0.692 * Non-intentional Walks + 0.722 * Hit by Pitch + 0.879 * Singles + 1.242 * Doubles + 1.568 * Triples + 2.007 * Home Runs) / (At Bats + Walks + Intentional Walks + Sacrifice Flies + Hit by Pitch)
What Is a Good wOBA?
The average wOBA in MLB changes every year, but the average wOBA is generally around 0.320. So, a good wOBA is anything above .320, and the higher, the better.
The best offensive players have wOBAs over 0.400. As we detail later in the article, the players with the highest wOBAs in MLB for the 2021 season and career leaders all have wOBAs over 0.400.
What Is a Bad wOBA?
A bad wOBA is less than the average of 0.320, and the lower it is, the worse the player is at reaching base and helping their team score runs. The worst wOBAs are 0.300 or lower, and players with wOBAs around these numbers aren’t good offensive players. They are bad at reaching base and producing runs.
Is wOBA a Good Stat?
wOBA is a good stat because it measures how often a player reaches base and how that player reaches base.
wOBA is important because it gives a different value to each way to reach on base, so certain methods have more weight and, therefore, more impact on a player’s wOBA. Home runs have the highest wOBA value, so the more home runs a player has, the higher their wOBA.
Comparing wOBAs between players and teams is one of the best stats to determine how efficient a team or player is at reaching base for each at bat they have. Higher wOBAs mean players are getting more bases per at bat, leading to more runs.
Is wOBA Better Than OPS?
wOBA and OPS both measure how effective a batter is at reaching base. But, wOBA is better than OPS because it’s a more accurate measurement since it considers how the batter reaches the base.
wOBA Career Leaders
Career wOBA includes all walks, hit by pitches, hits, and plate appearances throughout a player’s entire career in MLB.
Here are the MLB Career wOBA leaders from Stat Muse:
| Player | Career wOBA | |
| 1 | Babe Ruth | .513 |
| 2 | Ted Williams | .493 |
| 3 | Lou Gehrig | .477 |
| 4 | Jimmie Foxx | .460 |
| 5 | Rogers Hornsby | .459 |
| 6 | Hank Greenberg | .453 |
| 7 | Ty Cobb | .445 |
| 8 | Joe Jackson | .443 |
| 9 | Joe DiMaggio | .439 |
| 10 | Tristram Speaker | .436 |
| 11 | Dan Brouthers | .436 |
wOBA Season Leaders
A player’s season wOBA takes all their hits, walks, hit by pitches, and plate appearances for an entire season.
Here are the 2021 MLB wOBA leaders per Baseball Savant:
| Player | 2021 wOBA | |
| 1 | Bryce Harper | .431 |
| 2 | Juan Soto | .420 |
| 3 | Byron Buxton | .419 |
| 4 | Vladimir Guerrero Jr. | .419 |
| 5 | Ronald Acuña Jr. | .412 |
| 6 | Brandon Belt | .406 |
| 7 | Frank Schwindel | .403 |
| 8 | Jesse Winker | .403 |
| 9 | Fernando Tatis Jr. | .403 |
| 10 | Yasmani Grandal | .402 |
What Is XwOBA?
Expected weighted on-base average, or xwOBA is the projected wOBA for a player. But it doesn’t always end up being the wOBA that a player ends up with for the season. And, the actual wOBA can be higher or lower than the xwOBA.
The xwOBA is projected based on the exit velocity, the launch angle, and the sprint speed of hit balls by a player. Calculating xwOBA started in 2015 thanks to Statcast.
Here is MLB’s official definition of xwOBA:
Expected Weighted On-base Average (xwOBA) is formulated using exit velocity, launch angle and, on certain types of batted balls, Sprint Speed.
In the same way that each batted ball is assigned an expected batting average, every batted ball is given a single, double, triple and home run probability based on the results of comparable batted balls since Statcast was implemented Major League wide in 2015. For the majority of batted balls, this is achieved using only exit velocity and launch angle. As of 2019, “topped” or “weakly hit” balls also incorporate a batter’s seasonal Sprint Speed.
Knowing the expected outcomes of each individual batted ball from a particular player over the course of a season — with a player’s real-world data used for factors such as walks, strikeouts and times hit by a pitch — allows for the formation of said player’s xwOBA based on the quality of contact, instead of the actual outcomes. Likewise, this exercise can be done for pitchers to get their expected xwOBA against.
While xwOBA and wOBA may seem like the same stat, they are different because xwOBA doesn’t have any defensive factors.
For example, suppose a player hits a ball that should be a double based on velocity and launch angle, but the center fielder makes an impressive play to catch the ball. wOBA wouldn’t include this in its calculation except for being included as an at-bat. But, xwOBA would include the hit as a double in its calculation since it’s based on the player’s ability to hit and ignores defense.
Here is the MLB’s formula for calculating xwOBA:
All hit types are valued in the same fashion for xwOBA as they are in the formula for standard wOBA: (unintentional BB factor x unintentional BB + HBP factor x HBP + 1B factor x 1B + 2B factor x 2B + 3B factor x 3B + HR factor x HR)/(AB + unintentional BB + SF + HBP), where “factor” indicates the adjusted run expectancy of a batting event in the context of the season as a whole. The factors used in calculating xwOBA are the same ones used in the wOBA formula.
wOBA vs OPS
OPS (on-base plus slugging) and wOBA are stats that determine how good a player is at reaching base. As we know, wOBA considers how often a player gets on base, and how they got there.
On the other hand, OPS doesn’t consider how they got on base. OPS is a measurement of on-base percentage and slugging percentage. When calculating OPS, the different types of hits aren’t weighted like they are when calculating wOBA.
OPS does consider extra-base hits since it includes slugging percentage, which calculates how many extra-base hits a batter has. But, it only considers the number of bases per hit, not by any weighted factors for how many runs scored as wOBA does.
wOBA vs OBA
Both wOBA and OBA measure how good a player is at reaching base. But, wOBA gives more weight to different hits depending on how many runs are scored on average as a result of each hit.
OBA only considers how often a player reaches base per the number of at bats they have and not how many bases they got on each hit. So, unlike wOBA, a walk, a hit by pitch, a single, a double, a triple, and a home run all have the same weight in calculating OBA.
So, suppose two players both have five at bats in a game with no walks, hit by pitches, or sacrifice flies. One player has three home runs, and the other has three singles. Both players would have the same OBA of 0.600 for the game.
But, the player with the home runs would have a significantly higher wOBA for the game since home runs are weighted higher than singles.