From batting average to WAR, the box score is packed with acronyms. Here is a plain-English guide to the stats that describe the game, what each one measures and why it matters, so the next broadcast or box score reads a little clearer.
Hits divided by at-bats. A .300 average means the hitter gets a hit in 30 percent of at-bats that do not end in a walk, hit-by-pitch, or sacrifice.
Why it mattersThe oldest and most familiar hitting stat. It is easy to understand, but it ignores walks and treats a single the same as a home run, so it tells only part of the story.
How often a hitter reaches base per plate appearance, counting hits, walks, and hit-by-pitches. Reaching base on an error or fielder's choice does not count.
Why it mattersOuts are the scarcest resource in baseball. A hitter who avoids making outs, even by drawing walks, keeps innings alive, which is why OBP predicts run scoring better than batting average.
Total bases divided by at-bats. A single is one base, a double two, a triple three, a home run four, so it measures power, not just frequency of hits.
Why it mattersIt captures the value of extra-base hits that batting average flattens. A .500 slugging percentage signals real thump in the lineup.
On-base percentage added to slugging percentage. It combines the two halves of hitting, getting on base and hitting for power, into one number.
Why it mattersA quick, single-number snapshot of a hitter's overall offensive value. An OPS around .800 is solid, and .900 or above is star territory.
Slugging percentage minus batting average. It strips out singles to isolate a hitter's raw extra-base power.
Why it mattersIt answers a specific question: when this player makes contact, how much damage does he do? A high ISO marks a genuine power threat.
The share of plate appearances that end in a walk.
Why it mattersIt reflects plate discipline and a hitter's eye. A high walk rate raises on-base percentage even during a batting slump.
The share of plate appearances that end in a strikeout.
Why it mattersStrikeouts guarantee an out with no chance of advancing runners. A low strikeout rate signals a contact hitter, while a high one can still be acceptable if power and walks are strong.
The number of runs that score as a direct result of a hitter's plate appearance, such as a hit, a walk with the bases loaded, or a sacrifice fly.
Why it mattersA traditional counting stat that rewards driving runners home, but it depends heavily on teammates getting on base first, so it says as much about the lineup as the hitter.
The sum of bases a hitter earns on hits: one for a single, two for a double, three for a triple, and four for a home run.
Why it mattersIt is the raw material behind slugging percentage and a simple way to measure the volume of damage a hitter produces.
The average number of earned runs a pitcher allows per nine innings. Runs that score because of fielding errors are unearned and do not count.
Why it mattersThe classic measure of run prevention. It is intuitive, but it is influenced by defense and luck, which is why analysts pair it with fielding-independent stats.
The sum of walks and hits allowed, divided by innings pitched. It measures how many baserunners a pitcher permits each inning.
Why it mattersBaserunners lead to runs. A WHIP near 1.00 means the pitcher allows about one baserunner per inning, which is elite.
The average number of strikeouts a pitcher records per nine innings pitched.
Why it mattersIt measures raw swing-and-miss ability. Strikeouts are valuable because they remove the defense from the equation entirely.
The average number of walks a pitcher issues per nine innings pitched.
Why it mattersIt measures control. Free passes put runners on base without the hitter earning it, so lower is almost always better.
Strikeouts divided by walks. It compares a pitcher's best outcome against his worst self-inflicted one.
Why it mattersIt is one of the most stable indicators of pitching skill. A ratio above 3.0 usually points to a pitcher in strong command of his craft.
A start in which the pitcher completes at least six innings and allows three or fewer earned runs.
Why it mattersIt rewards a starter for going deep and keeping his team in the game, unlike the win, which depends on run support and the bullpen.
Credited to a relief pitcher who finishes a game his team wins while protecting a narrow lead, most commonly a lead of three runs or fewer entering his outing.
Why it mattersIt is the headline stat for closers, though it is situational: a pitcher only earns saves when handed the right ninth-inning lead.
Credited to a relief pitcher who enters in a save situation, records at least one out, and hands off the lead without giving it up.
Why it mattersIt is the setup man's version of the save, recognizing the middle-relief work that bridges the starter to the closer.
A start in which one pitcher records every out for his team, pitching the entire game.
Why it mattersOnce routine, it is now rare in an era of pitch counts and specialized bullpens, which makes it a marker of durability and dominance.
A complete game in which the pitcher allows the opposing team zero runs.
Why it mattersIt is the gold standard of a dominant start: nine innings, no runs, no relief help.
OPS adjusted for the ballpark a player calls home and the run-scoring environment of the league, then scaled so that 100 is exactly league average.
Why it mattersIt lets you compare hitters across different eras and ballparks. A 130 OPS+ means 30 percent better than league average, whether it was 1929 or today.
An all-in-one offense metric that weights every outcome by its actual run value, adjusts for park and league, and scales so 100 is league average.
Why it mattersMany analysts consider it the best single measure of a hitter's total offensive contribution. Like OPS+, a reading of 120 means 20 percent above average.
An estimate of what a pitcher's ERA should look like based only on the outcomes he controls: strikeouts, walks, hit-by-pitches, and home runs. It is scaled to look like ERA.
Why it mattersDefense and batted-ball luck can distort ERA. FIP isolates the pitcher's own contribution, so it often predicts future ERA better than past ERA does.
Batting average calculated only on balls hit into the field of play, excluding home runs and strikeouts. It measures how often batted balls become hits.
Why it mattersIt is a key luck indicator. A hitter or pitcher with a BABIP far from the roughly .300 league norm is often due to regress toward average.
An attempt to sum up a player's total value, hitting, baserunning, fielding, and pitching, into one number: how many more wins he is worth than a freely available replacement-level player.
Why it mattersIt is the closest thing to a single all-encompassing value stat. Different sites calculate it slightly differently, so it is best used for broad tiers rather than tiny gaps.
A fielding metric that estimates how many runs a defender saves or costs his team compared with an average player at the same position, based on the plays he makes and misses.
Why it mattersDefense is hard to capture in traditional stats. UZR is one attempt to put a run value on glovework, though it needs multiple seasons to stabilize.
A fielding metric that tallies the runs a defender saves or costs relative to average across every aspect of defense, expressed in runs.
Why it mattersLike UZR, it translates fielding into the common currency of runs, making it possible to compare a glove-first player's defense against a slugger's bat.
The speed of the baseball as it leaves the bat, measured in miles per hour by tracking technology.
Why it mattersHard contact leads to more hits and more power. A consistently high exit velocity signals a hitter squaring the ball up, even when the results have not caught up yet.
The vertical angle at which the ball leaves the bat. Ground balls have low angles, line drives and fly balls higher ones.
Why it mattersPaired with exit velocity, it explains outcomes. Hard contact in the ideal angle range produces the line drives and fly balls that become extra-base hits.
When a baserunner advances to the next base on his own during a pitch or play, without the help of a hit, walk, or error.
Why it mattersIt reflects speed and instincts and can turn a single into scoring position, though a caught stealing costs a valuable out.
When a runner attempting to steal is tagged out before reaching the next base.
Why it mattersIt is the cost side of the stolen-base ledger. A high success rate is needed for base stealing to be worth the risk of giving away outs.
Any completed turn at bat, including those that end in a walk, hit-by-pitch, or sacrifice, unlike an at-bat, which excludes those outcomes.
Why it mattersIt is the truest denominator for rate stats because it counts every trip to the plate, which is why walk rate and strikeout rate use it.
Ready to put these stats in context? Walk the franchise story in the Athletics history archive or trace every move from Philadelphia to Las Vegas on the franchise timeline.
LV Athletics is an independent fan site and is not affiliated with the Athletics or Major League Baseball.