wOBA
Weighted On-Base Average (wOBA) is one of the most important and popular catch-all offensive statistics. It was created by Tom Tango (and notably used in “The Book”) to measure a hitter’s overall offensive value, based on the relative values of each distinct offensive event.
wOBA is based on a simple concept: Not all hits are created equal. Batting average assumes that they are. On-base percentage does too, but does one better by including other ways of reaching base. Slugging percentage weights hits, but not accurately (Is a double worth twice as much as a single? In short, no). On-base plus slugging (OPS) does attempt to combine the different aspects of hitting into one metric, but it assumes that one percentage point of SLG is the same as that of OBP. In reality, a handy estimate is that OBP is around twice as valuable than SLG (the exact ratio is x1.8).
Weighted On-Base Average combines all the different aspects of hitting into one metric, weighting each of them in proportion to their actual run value. While batting average, on-base percentage, and slugging percentage fall short in accuracy and scope, wOBA measures and captures offensive value more accurately and comprehensively.
The wOBA formula for the 2011 season was:
wOBA = (0.69×uBB + 0.72×HBP + 0.89×1B + 1.26×2B + 1.60×3B +
2.08×HR + 0.25×SB -0.50×CS) / PA
These weights change on a yearly basis, so you can find the specific wOBA weights for every year from 1871 to 2010 here.
Context:
Please note that the following chart is meant as an estimate, and that league-average wOBA varies on a year-by-year basis. It is set to the same scale as OBP, so league-average wOBA in a given year should be very close to the league-average OBP. To see the league-average wOBA for every year from 1901 to the present, check the FanGraphs leaderboards.
Rules of Thumb
| Rating | wOBA |
|---|---|
| Excellent | 0.400 |
| Great | 0.370 |
| Above Average | 0.340 |
| Average | 0.320 |
| Below Average | 0.310 |
| Poor | 0.300 |
| Awful | 0.290 |
Things to Remember:
● This stat accounts for the following aspects of hitting: unintentional walks, hit-by-pitches, singles, doubles, triples, homeruns. Stolen-bases and caught stealing numbers are also sometimes included. One reason to leave SB and CS out of the equation is if you are using wOBA to determine an ideal batting lineup.
● Exactly how much to weigh each of the components of wOBA was determined using linear weights.
● wOBA can be converted into offensive runs above average easily. These are called Weighted Runs Above Average (wRAA). The formula to convert wOBA into wRAA is listed below:
wRAA = ((wOBA – league wOBA) / wOBA scale) × PA
(league-average wOBA can be found here; wOBA scale values can be found here)
● This stat is context-neutral, meaning it does not take into account if there were runners on base for a player’s hit or if it was a close game at the time.
● wOBA on FanGraphs is not adjusted for park effects, meaning that batters that play in hitter-friendly parks will have slightly inflated wOBAs.
Custom wOBA and Linear Weights for 1871-2010 – Beyond the Box Score
Calculating wOBA (Datebasa Version) – The Book Blog
A Visual Look at wOBA – FanGraphs
4
Heads up, the link to the wOBA calculator is broken (delete the “0″ after “spreadsheets” in the URL).
Besides that, this entire saber library is amazing work, Steve.
Thanks…it should be fixed now. Hopefully that works.
It could be user error, but I believe the “calculator” is view-only.
All right, it’s public on the web now. The only trick is if you want to edit it, you need to save your own copy and do it that way. I want to make sure the formula stays intact and it doesn’t get changed by accident.
I’m still having some difficulty with this. It doesn’t look like it’ll let me save it…
Haha, dang, why do I suck so much at this? Now it’s public and anyone can edit. Hopefully that does the trick.
Yeah it’s working, except now it looks like if there is more than one person viewing the document, that they can potentially both be punching in their own numbers at the same time.
Geez. Okay, I’ll mess around with it some tonight.
No sweat. Looking forward to having that here though
Oooo. A fourth tier of responses. Should be global.
Apologies if I’m being a bit lazy, cause I’m sure this answer is somewhere in this excellent library, but why are HBP weighted more than NIBB (.75 v .72)?
HBPs have a slightly better linear weighting than do NIBBs. The reason for this is that pitchers have somewhat more control over NIBBs, and thus they are more frequent in those situations in which their impact is somewhat lessened (e.g., runners on second and/or third, first base open) and less frequent when their impact is greatest (e.g., bases loaded).
Excellent, thank you
a HBP also mens that the pitcher is more likely to be wild.
The 25th percentile wOBA is really only .004 below the 50th percentile, but the 75th percentile is .045 above? It doesn’t make intuitive sense that such a large number of players would be bunched just below the 50th percentile but not just above it.
This graph is for WAR, but the same general concept is the same. There’s a big bunch of mediocre players once you get to a certain level.
http://assets.sbnation.com/assets/483944/war_distro_2010.jpg
Also, this is why I call these “estimates”. Technically the 50th percentile is a bit higher than what’s listed, but I wanted to express the mean instead of the 50th percentile. Makes it a tad weird.
I don’t see in player’s stats the number of times they reached base on an error.
Where can one find the Reached on Error stats for individual players?
Perhaps I missed something but I did my own calculation for a specific player, Ian Kinsler, and came out a little off. Do the linear weights change from year to year?
Q#1: why is this called weighted-onbase-AVERAGE? This is not an average.
If this is an average, what does 1.000 represent (other than awesome!)? what does Ellsbury’s 0.402 2011 wOBA mean? he’s just over 40% of what?
Q#2: Who came up with the name? Do you really think people want to use this in public (man, have you seen his woba)?
I love the stat itself. Love the concept. And what you guys have done to provide us with great tools for analysing players performances, but Im not going to use a stat that sounds like a drunk jedi knight (Obi-woba kenobi?)
Q#3: why is this matched up to look like OBP numbers? Isnt this a kind of replacement for slugging% (which also isnt a percentage)?
what is the fascination with creating new stats and then trying to make them look like other stats? I believe the idea is that your afraid if you keep creating new stats with new numbers, we’ll get fed-up. We’re baseball-fanatics… we’ll never get fed-up of these numbers! I think the opposite has happened, as I for one don’t like viewing a new stat that just hides itself behind the appearance of an old one. Give them there own individual look and they’ll be more widely accepted.
Im currently taking your wOBA results and multipling them by 1.4271886648681 (as close as I can get it without knowing ‘reached base on error’ results) so that 1.000 matches up with the greatest single season performance ever – Babe Ruth in 1921 – and Ive called the stat BRaverage (pronounced brave-erage), meaning the Babe Ruth average. The numbers now have a meaning. How close is the player to the greatest ever season? Jacoby Ellsbury? in 2011 scored 0.574 in BRaverage.
Of course, using Babe Ruths 1921 season is just an example, but my point is, lets make these stats express a point, have some kind of scale that we understand… And a name we can all pronounce (publically and literally) – though BRaverage could also be shortened to BRA, which might be even more publically embarrassing… have you seen Prince Fielders BRA?
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I don’t understand why wOBA doesn’t consider intentional walks. It’s especially confusing since hit by pitch is considered. I’d think if HBP is factored in, so would intentional walks. What am I missing?
my guess would be because IBB are from your teammates putting the other team in position where it is better to put you on base, and this is supposed to try to determine what an individual is doing at the plate by himself.
But then HBP and reaching on an error shouldn’t count either. (which they probably shouldn’t.)
I was a major STAThead back in the late 80s and early 90s before it became semi-mainstream thanks to Internet and Moneyball. Just getting back into it. I developed my own metrics in the past and wonder why some stats are included/excluded here. Maybe I just haven’t thought it through:
Why is RBOE relevant? If the player “should” have been out, why reward him? That may be useful for comparing projected versus actual run totals for past seasons, but it does nothing for player evaluation or projecting the future.
SF should have some value if a HBP has more value than a NIBB. As it is a byproduct of a situational at bat just as a NIBB might be.
SH is and should be excluded as that is an extreme situation just as a IBB.
Why do all these metrics ignore SB and CS? They are readily available offensive stats and quite meaningful for a handful of players.
Why are Ks and GIDP excluded? They should both have a negative value.
The only rationale for excluding the above I can see is that the wOBA is simply an attempt to combine two imperfect stats (OBP and SLG). Why not go the extra step and create a single number that estimates the total offensive value of a hitter…
Since the formula does not give any credit for intentional walks, shouldn’t you divide by plate appearances minus intentional walks instead of just dividing by plate appearances? Otherwise you are actually punishing a batter who gets intentionally walked. Or am I missing something?
I am surprised that HBP are weighted higher than walks in the formula, since getting beaned is more a function of luck than drawing a walk. True, some guys get beaned more, but it’s not a repeatable skill like walking is.