wOBA Explained: Weighting Every Way to Reach Base

By 4Baseball Staff · November 5, 2026 · 10 min read

Weighted on-base average counts a walk, single, double, triple and home run at their real run values. This guide covers the formula, linear weights, two worked examples and how to read the number.

Weighted on-base average, or wOBA, is a rate statistic that tries to answer one question: how much did a hitter's plate appearances add to his team's run total, per plate appearance? It does that by giving each way of reaching base its own weight, based on how many runs that event is worth, and then dividing by opportunities. The result is scaled to look like on-base percentage, so a .320 wOBA reads like a .320 OBP, but it is a better measure of offense because it does not treat a walk, a single and a home run as equal events.

The statistic was introduced by Tom Tango in The Book: Playing the Percentages in Baseball (2006), which he wrote with Mitchel Lichtman and Andrew Dolphin. It descends from the older work on linear weights by George Lindsey in the 1960s and by Pete Palmer and John Thorn in The Hidden Game of Baseball (1984). Those authors found that the run value of each batting event could be estimated from play-by-play data, and Tango packaged those values into a single rate.

This guide explains where the weights come from, writes out the formula, works two examples with a calculator-friendly set of numbers, and says what the statistic leaves out. If you want one number that captures a hitter's contribution before park and league adjustments, wOBA is the one to learn first.

The problem with batting average and OPS

Batting average counts every hit as one and ignores walks. On-base percentage counts walks, hits and hit-by-pitches as one, and ignores how many bases a hit gained. Slugging percentage counts total bases and ignores walks. Each of them leaves out part of the picture, which is why people combined two of them into OPS, on-base plus slugging.

OPS is a useful shortcut, and a separate guide covers OPS and OPS+. But it adds two numbers with different denominators and different scales, and by most estimates it undervalues on-base ability. A point of OBP is worth more than a point of slugging in run terms, by a factor that studies put at somewhere around 1.7 to 1.8, while OPS counts them the same. A hitter who walks a lot and hits for modest power is scored lower by OPS than his run production deserves, and a free swinger with power is scored higher.

Slugging percentage also has a structural problem. It scores a single as 1, a double as 2, a triple as 3 and a home run as 4. Those are the number of bases, and the base count is not the same as the run value. A home run is worth about 2.4 times a single in actual run value, not 4 times. A walk, which slugging ignores entirely, is worth about three-quarters of a single. The weights in wOBA correct both distortions at once. For background on the traditional triple-slash measures, see the guide to batting average, on-base percentage and slugging.

The idea: every event has a run value

The starting point is run expectancy. At any moment in an inning there are 24 possible situations, made up of eight arrangements of runners on base and three numbers of outs. Using many seasons of play-by-play data, researchers can compute the average number of runs scored from each situation to the end of the inning. With nobody on and none out, a team scores about half a run on average over the rest of the inning. With the bases loaded and none out, the figure is more than two runs.

An event changes the situation, and the change in expected runs, plus any runs that scored on the play, is the run value of the event. A single with the bases empty moves the team to a runner on first and increases the expected runs by a certain amount. The same single with a runner on second might score a run. Averaged over all the base-out situations in which singles happen, a single is worth a particular number of runs. The same procedure applied to each event gives the values of a walk, a hit by pitch, a double, a triple, a home run and an out.

These averages are called linear weights, because the total run value of a batter's season can be estimated as a linear sum: so many runs per single times the number of singles, plus so many per double times the number of doubles, and so on. The value of an out is negative, relative to the average event. The weights depend on the run environment, so they change each year. When scoring is high, a run is worth less, and each hitting event is worth a bit less relative to an out.

From run values to wOBA

Run values are not on the same scale as OBP, so Tango did two things. First, he shifted the weights so that the value of an out is zero, which means that every other event has a positive weight. Second, he scaled the weights so that the league average wOBA equals the league average OBP in that season. The result is a number that reads like OBP, which makes it easy to judge. A .400 wOBA is excellent for the same reason that a .400 OBP is, and a .300 wOBA is weak.

The formula for a season is:

wOBA = (wBB × uBB + wHBP × HBP + w1B × 1B + w2B × 2B + w3B × 3B + wHR × HR) ÷ (AB + BB − IBB + SF + HBP)

Here uBB is unintentional walks, which means walks minus intentional walks, and each w is the weight for that year. The denominator is plate appearances without intentional walks and sacrifice bunts. Intentional walks are left out because they are usually the manager's choice, handed out in situations where the batter did not create the opportunity. Sacrifice bunts are left out because they are also a managerial decision, and sacrifice flies stay in because the batter hit the ball in play and made an out in the ordinary way.

Reaching base on an error is not counted, because the batter did nothing to earn the extra base. Stolen bases and caught stealing are not part of wOBA either. Baserunning has its own run values, and the stat sites that publish wOBA keep that value separate, so that offense and baserunning can be added together later.

A table of weights

The exact weights depend on the season. The table below gives a typical set, rounded to three decimals, of the kind published for a recent-era season. Treat them as illustrations of the relative sizes, not as the figures for any particular year.

Several relationships stand out. A hit by pitch and a walk are close in value, because both put the batter on first base. A walk is worth about 78 percent of a single (0.690 divided by 0.888). A double is worth about 1.4 singles, a triple about 1.8 singles and a home run about 2.4 singles. These ratios are much flatter than the 1-2-3-4 progression of slugging, and they explain why walks and singles matter more in wOBA than in OPS.

Worked example one: a full season

Take a hitter with 500 at-bats and the following season: 95 singles, 30 doubles, 3 triples and 22 home runs, for 150 hits. He has 60 walks, 5 of them intentional, 5 hit-by-pitches and 5 sacrifice flies. His traditional line is .300 for average, .377 for on-base percentage and .504 for slugging, an OPS of .881.

The unintentional walks are 55. The numerator is the sum of each count times its weight:

• Walks: 55 × 0.690 = 37.95
• Hit by pitch: 5 × 0.722 = 3.61
• Singles: 95 × 0.888 = 84.36
• Doubles: 30 × 1.271 = 38.13
• Triples: 3 × 1.616 = 4.85
• Home runs: 22 × 2.101 = 46.22

The total is about 215.12. The denominator is 500 plus 60 minus 5 plus 5 plus 5, which is 565. Dividing gives a wOBA of about .381. On a scale where .320 is roughly average, that is a very good hitter.

To turn the rate into runs, subtract the league average wOBA, divide by the scale factor, and multiply by plate appearances. This gives weighted runs above average, or wRAA. If the league average were .315 and the scale factor were 1.25, both used here only for illustration, the hitter's wRAA would be (.381 − .315) ÷ 1.25 × 570 plate appearances, or about 30 runs. A common rule of thumb is that ten runs equal one win, so he would be worth about three wins on offense alone, before any adjustment for park, position or defense.

Worked example two: when OPS and wOBA disagree

The clearest reason to use wOBA is that it can separate two hitters whom OPS rates as equal. Consider two players, each with 600 plate appearances and each at an OPS of .800.

Player A is the power hitter who rarely walks, and Player B is the patient hitter with less power. OPS calls them a tie. wOBA gives Player B an edge of about eleven points, because his 60 extra walks are worth more than A's 12 extra home runs, 8 extra singles and 2 extra doubles once the real run values are applied. Using the same illustrative scale factor of 1.25, eleven points of wOBA over 600 plate appearances is about five runs a season, or half a win. That is not a vast gap, and it is the kind of difference that appears when a decision is close, such as choosing between two similar hitters for a roster spot.

The exercise also shows what wOBA does not do. It does not say that walks are better than home runs. A power hitter still creates a lot of offense, and if Player A had walked 40 times instead of 30 he would have caught up. What the statistic does is price each outcome in runs, so that the tradeoffs come out in the right ratios.

Reading a wOBA

Because the statistic is scaled to OBP for the league and year, the average moves with the run environment. In recent seasons the league average has been near .310 to .320. The table gives rough guidelines for a typical recent season.

These bands are guidelines. Compare a player's wOBA to the league average for that season, and be careful with comparisons across eras unless the number has been adjusted. That is the purpose of wRC+, which sets the league average at 100 and adjusts for ballpark. The wRC+ guide shows how that conversion works, and it is built from wOBA.

Seasons from before 1950 can be scored with the same formula when the records are complete, but intentional walks and some other events were not always recorded, so treat old wOBA figures as estimates. The traditional numbers for a player such as Joe DiMaggio are easier to verify.

What wOBA leaves out

The first limit is the park. A hitter in a ballpark that favors offense gets a boost, and a hitter in a pitcher's park loses some. wOBA does not correct for that, so a raw wOBA is not a full measure of skill. The second limit is context. All singles carry the same weight regardless of the situation. A single with the bases loaded is worth more in practice than a single with the bases empty, and wOBA averages those cases. Measures that account for the situation exist, but they describe what happened more than what the hitter will do.

The third limit is everything but hitting: defense, baserunning and the positional adjustment are all outside the statistic. A catcher with a .330 wOBA and a first baseman with a .330 wOBA have the same offensive rate, but their overall value differs. The fourth limit is the sample. Like any rate, wOBA is noisy over a few weeks. A hitter's batting average on balls in play is the usual source of the noise, a topic covered in the BABIP guide.

A fifth point applies to power: isolated power tells you how much of a hitter's value comes from extra bases, while wOBA tells you the total. Used together they show whether a high wOBA rests on power, on patience or on contact.

Expected wOBA

The Statcast system publishes a related figure called expected wOBA, or xwOBA. Instead of counting the actual results of each batted ball, it assigns each ball an expected outcome based on its exit velocity and launch angle, and in some versions the batter's sprint speed. The expected result is converted to the same wOBA scale. The number answers a different question: what would a hitter's wOBA have been if his batted balls had produced the average result for balls hit like that? It is a tool for separating skill from luck, and it is only available for the Statcast era, which begins in 2015.

Common questions

Is wOBA better than OPS? For measuring offensive production per plate appearance, yes, because it uses run values for each event. OPS is simpler and good enough for a quick look. The two usually agree within a few points of ranking.

Why do the weights change every year? Because the run environment changes. When teams score more, a single is worth slightly less relative to an out, and the scale factor changes too. The sites that publish the statistic update the weights each season.

Does wOBA include stolen bases? No. Stolen bases and caught stealing have separate run values, and they enter overall measures such as wins above replacement through baserunning components.

What is a good wOBA? About .320 is average in recent seasons, .340 or higher is above average and .370 or higher is excellent. Check the league average for the season you are looking at.

Can I compute it myself? Yes. The box score gives walks, hit by pitches, singles, doubles, triples and home runs, and the stat calculator on this site handles the traditional rates. You need the season's weights from a published table for the exact wOBA.

Where to go next

If you want the park-adjusted version, read wRC+ explained. If you want to see why wOBA reacts to luck, read BABIP explained. The leaders page lists the current league leaders in the traditional categories, and for how the postseason adds another layer of context to a hitter's numbers, see how the MLB postseason works.