Thus, we grade wOBA the same way as OBP:
0.310 and below is under average
0.320 is marginally average
0.330 is average
0.340 is slightly above average
0.350 is good
.360 and above is very good

A player’s wOBA may or may not be the same as their OBP.

If that’s the case, then why go through all this trouble. Why not just check OBP?!

The pro is it makes perfect sense. It’s based on linear weights to particular statistics. EqA is weirdly constructed.

The con is, it’s weak in the points where EqA is strong: comparing across eras, and park adjustments.

Fortunately, fangraphs also now includes adjusted weighted runs created, or wRC+. You’re probably familiar with OPS+. This is kind of the same thing, only a lot more detail and accurate (in that OPS+ overrates low OBP, big HR total sluggers like Gary Gaetti, and underrates guys who succeeded by maintaining a high OBP, or base stealers, like Tim Raines and Rickey Henderson).

To put it back to Williams for a second, his career wRC+ was 128. Essentially saying he was a 28% better than average hitter in his career. Which is good. But it’s also the same wRC+ as Al Ferrara (.346 in a short career in a pitchers era) and Rick Monday (.358 wOBA). Also just one behind Hank Sauer (.380 wOBA in an extreme hitter’s era).

But yeah, to sum up your original question, wOBA is everything contributed by a hitter, scaled into a number equivalent to the league average OBP for that season. Good number to see how much a player produced in a season, just not recommended as a 1:1 comparison for a Rockie and a Padre (use wRC+ for that). Good example is how Carlos Gonzalez edged Kyle Blanks in wOBA .378 to .372, but Blanks crushed CarGo in wRC+, 138 to 125.

wOBA gives proper weight to all the things a hitter can do to produce value, and is a more accurate reflection of a hitter’s value. a home run is worth a little more than twice as much a single

I skipped a step — when calculating the wOBA rate stat, the linear weights values are already multiplied by a “wOBA scale,” (e.g, 1.15, 1.2, whatever) so when you convert to a runs scale, you need to divide it back.

I believe (correct me if I’m wrong) that FanGraphs uses a custom linear weights version of wOBA that 1) calculates the specific value of each event in a given year, and 2) alters the “wOBA scale” (the “1.15″ in the original formula) so that league average wOBA = league average OBP. So the wOBA scale in recent years has been more like 1.2.

Hope that helps.