wOBA (Weighted On-Base Average) measures a hitter's offensive value by assigning empirically derived run values to every way of reaching base. A home run is worth roughly 2.10, a double about 1.27, a single about 0.89, and a walk about 0.69. Those aren't guesses, derived from historical data measuring how often each event actually leads to runs. League average wOBA is typically around .320. It's scaled to look like on-base percentage, so the numbers are immediately readable.
What's Wrong With the Stats We Already Have
To understand why wOBA exists, you have to understand what the traditional stats get wrong. This isn't about dismissing batting average or OBP. It's about knowing their limits.
Batting average counts only hits and treats them all identically. A bloop single and a 450-foot home run are both just "1." It ignores walks entirely. It has no opinion about doubles versus triples. It's measuring something real, contact, but it's throwing away most of the information in the process.
On-base percentage is better. It adds walks and hit-by-pitches to the picture. But it commits the same mistake batting average does with hits: a walk counts the same as a home run. Both put a runner on base, but they don't produce runs at anything close to the same rate.
Slugging percentage tries to fix the hits problem by using total bases. A single is 1, a double is 2, a triple is 3, a home run is 4. But those multipliers aren't right either. A home run isn't worth exactly four singles in run-production terms. And slugging ignores walks completely.
OPS combines on-base and slugging and gets closer, but it adds two things that aren't measured on the same scale and treats a point of OBP as equal to a point of SLG. That's not accurate. OBP is roughly twice as valuable in run-creation terms.
wOBA starts over from scratch and does it right.
"Not all hits are created equal. wOBA is the stat that finally takes that seriously."
The Baseball NerdHow wOBA Actually Works
wOBA was created by sabermetrician Tom Tango and introduced in The Book: Playing the Percentages in Baseball (2006). The core idea is straightforward: instead of counting events or weighting them by total bases, assign each offensive event the actual run value it produces based on historical data.
Those run values come from something called run expectancy: a table built from decades of play-by-play data that shows how many runs a team is expected to score given any combination of base runners and outs. When a batter hits a double with nobody on and one out, the run expectancy changes by a specific amount. That change, averaged across thousands of similar situations, becomes the weight for a double.
The result is a set of linear weights that look roughly like this in a typical season:
| Event | Weight | What This Tells You |
|---|---|---|
| Unintentional Walk | ~0.69 | Real value, often underrated |
| Hit By Pitch | ~0.72 | Slightly more than a walk |
| Single | ~0.89 | Baseline hit value |
| Double | ~1.27 | Not twice a single |
| Triple | ~1.62 | Not three times a single |
| Home Run | ~2.10 | Not four times a single |
Look at those numbers and a few things jump out. A walk is worth 0.69, not zero. A double is worth 1.27, not 2.00. A home run is worth 2.10, not 4.00. The whole idea that extra-base hits are worth a clean multiple of singles is wrong, and wOBA corrects it.
These weights are recalibrated every season. In a high-offense year, home runs are more common, so each individual one is slightly less scarce and worth a little less. In a pitching-dominated year, the home run weight goes up. FanGraphs publishes the exact coefficients for every season going back to 1871.
The Formula
Once you understand what the weights represent, the formula is just arithmetic:
÷ (AB + BB − IBB + SF + HBP)
uBB = unintentional walks | IBB = intentional walks (excluded) | SF = sacrifice flies
Intentional walks are excluded because they're a strategic decision by the defense, not a reflection of what the hitter did. Sacrifice flies are included in the denominator because the hitter used a plate appearance, even if they don't count as an at-bat.
A Worked Example
In 2013, Mike Trout had 100 unintentional walks, 9 HBP, 115 singles, 39 doubles, 9 triples, and 27 home runs. Plug those into the formula with that year's weights and you get a wOBA of .423. That's elite by any measure, which lines up with what we know about Trout in 2013.
9 HBP × 0.722 = 6.5
115 1B × 0.888 = 102.1
39 2B × 1.271 = 49.6
9 3B × 1.616 = 14.5
27 HR × 2.101 = 56.7
Total = 298.4
What Is a Good wOBA?
wOBA is deliberately scaled to look like on-base percentage. That means the numbers sit in a familiar range and are immediately readable without conversion.
| wOBA | Grade | Context |
|---|---|---|
| .400+ | Elite | All-Star caliber offensive season |
| .370–.399 | Great | Significantly above average |
| .340–.369 | Above Average | Solid everyday producer |
| .320–.339 | Average | League median range |
| .300–.319 | Below Average | Acceptable with elite defense |
| <.300 | Poor | Difficult to justify a roster spot |
League average floats slightly year to year, some seasons it runs a touch above or below .320, but the scale above holds across most modern eras. If you know what a good OBP looks like, you already know how to read wOBA.
wOBA vs. wRC+: Which One Should You Use?
This comes up constantly, and the answer is that they're not competing. wOBA is an input into wRC+. They answer slightly different questions.
The practical rule: use wOBA when you want to know how a hitter performed at the plate in a vacuum. Use wRC+ when you want to compare that performance to others across different environments. For most everyday analysis, wRC+ is the finished product. wOBA is the engine running underneath it.
wOBA's Honest Limitations
No stat does everything, and wOBA is upfront about what it doesn't cover.
It doesn't adjust for park or era. That's what wRC+ is for. A .380 wOBA at Coors Field, where the thin air and humidor create a hitter's paradise, is a different achievement than a .380 wOBA at Petco Park. wOBA doesn't know that. wRC+ does.
It slightly undervalues elite base stealers. A stolen base doesn't appear in the wOBA formula. A player who hits .260 but steals 60 bases is worth more to his team than wOBA captures.
It doesn't account for defensive position. A .330 wOBA from a catcher is a completely different roster asset than a .330 wOBA from a first baseman. wOBA is purely about what happens at the plate.
None of these are fatal flaws. They're just reasons why wOBA works best as part of a larger analytical picture. For total player value, WAR adds baserunning, defense, and positional adjustments on top of the offensive foundation that wOBA provides.
Frequently Asked Questions
Who created wOBA?
wOBA was created by sabermetrician Tom Tango and first published in The Book: Playing the Percentages in Baseball in 2006. It has since become one of the most widely used offensive metrics in baseball analytics and is the foundation for wRC+, which FanGraphs uses in their WAR calculation.
Why do the wOBA weights change every year?
The weights are derived from historical run expectancy data and recalibrated annually to reflect the current run-scoring environment. In a high-offense season, home runs are more common and slightly less scarce, so each one carries a marginally lower weight. In a low-offense season, the weights shift accordingly. FanGraphs publishes the exact coefficients for every season on their Guts! page.
Is wOBA better than OPS?
More precisely constructed, yes. OPS adds on-base percentage and slugging as equals, but OBP is roughly twice as valuable in run-production terms. wOBA uses actual run weights derived from play-by-play data. The two stats agree most of the time, with a correlation is very high, but wOBA handles edge cases more accurately, particularly for high-walk low-power hitters who tend to be undervalued by OPS.
Does wOBA include stolen bases?
No. wOBA measures only events that occur during a plate appearance. Stolen bases and caught stealing happen between plate appearances and aren't part of the formula. This is one of wOBA's acknowledged limitations, elite baserunners are slightly undervalued. Baserunning runs are added separately when calculating WAR.
Where can I find wOBA leaderboards?
FanGraphs maintains full MLB and MiLB wOBA leaderboards, searchable by season, career, team, and position. Baseball Savant also publishes wOBA alongside Statcast data including expected wOBA (xwOBA), which adjusts for contact quality on batted balls.