What the numbers mean

A passing efficiency rate that extends adjusted yards per attempt to count sacks: sack yardage is subtracted from the yards and sacks are added to the attempts, so a passer who takes sacks is charged for them. Touchdowns are credited at 20 yards and interceptions charged at 45, a

The NFL's official measure of passing efficiency, adopted by the league in 1973. It combines four per-attempt rates — completion percentage, yards per attempt, touchdown rate and interception rate — each scaled and capped so no single component can dominate. The result runs from

Shown on: NFL player profiles — passing table, column Rate

The simplest passing efficiency rate: a passer's gross passing yards divided by his pass attempts. In official NFL scoring a sack is not a pass attempt, and an individual passer's yards do not have sack yardage subtracted (team net passing yards do).

Shown on: NFL player profiles — passing table, columns Y/A and AdjY/A

Field-goal percentage adjusted for the extra point a three-pointer is worth: each made three counts as one and a half made field goals. Free throws are not included (true shooting percentage includes them).

Shown on: NBA player profiles — advanced table, column eFG%

John Hollinger's per-minute rating of a player's box-score production. It adds positive contributions (made shots, free throws, rebounds, assists, steals, blocks) and subtracts negative ones (missed shots and free throws, turnovers, fouls), weights each by its league-average valu

Scoring efficiency that counts two-pointers, three-pointers and free throws in one number: points scored per shooting possession, halved so it reads on the field-goal-percentage scale. The 0.44 multiplier on free-throw attempts estimates the share of free throws that end a posses

Shown on: NBA player profiles — advanced table, column TS%

An estimate of the share of his team's plays a player uses — ends with a shot attempt, a trip to the free-throw line or a turnover — while he is on the floor. Around 20% is average for a rotation player; a team's five players on the floor always sum to about 100%.

Shown on: NBA player profiles — advanced table, column USG%

A pitcher's ERA measured against the league ERA of the same season, scaled so 100 is league average and higher is better: an ERA+ of 150 means the league's ERA was 1.5 times the pitcher's. As published by Baseball-Reference it is also adjusted for ballparks.

OPS rescaled against the league average for the same season, so 100 is exactly league average and 150 means 50% better than average. Because each season is measured against its own league, OPS+ compares hitters across eras. As published by Baseball-Reference it is also adjusted f

Hits divided by at-bats — the oldest rate statistic in baseball. At-bats exclude walks, hit-by-pitches, sacrifice bunts, sacrifice flies and catcher's interference, so batting average measures only how often an official at-bat ends in a hit; it gives a single and a home run equal

Earned runs a pitcher allows per nine innings. Earned runs exclude runs the official scorer judges would not have scored without a fielding error or a passed ball. Innings are counted in outs, so 200.1 innings in baseball notation means 200⅓.

How often a batter reaches base by hit, walk or hit-by-pitch per opportunity. Unlike batting average it credits walks and hit-by-pitches, and its denominator includes sacrifice flies (but not sacrifice bunts). Reaching base on an error or a fielder's choice does not count.

On-base percentage plus slugging percentage — a one-number summary of a hitter's ability to reach base and to hit for power. Adding the two rates is a convenience rather than a weighted model (a point of OBP is worth more runs than a point of SLG), and OPS is not adjusted for lea

Total bases per at-bat — a power rate. A single counts one base, a double two, a triple three and a home run four, so slugging rewards extra-base hits that batting average treats like singles. Despite the name it is an average of bases, not a percentage.

Shown on: MLB player profiles — batting table, column SLG

The number of batters a pitcher puts on base by walk or hit per inning pitched. Hit-by-pitches, errors and fielder's choices are not counted, so WHIP is a measure of baserunners allowed through the pitcher's own walks and hits only.

An estimate of how many wins a player contributed beyond a freely available replacement-level player, combining batting, baserunning and fielding with an adjustment for position — or, for pitchers, run prevention.

Goals a goaltender allows per 60 minutes of playing time. Empty-net goals scored while the goaltender is off the ice are not charged to him. Because it counts goals rather than shots, GAA reflects the defence in front of the goaltender as well as the goaltender himself.

Shown on: NHL goaltender profiles — column GAA

The sum of a team's (or a player's on-ice) shooting percentage and save percentage, usually at five-on-five. Because league-wide shooting and save percentages must add up to 100%, PDO is centred on 100 (or 1000), and values far from it tend to regress — it is used as a rough indi

A skater's on-ice goal differential: plus one when he is on the ice for a goal his team scores at even strength or shorthanded, minus one when he is on the ice for an even-strength goal against or a shorthanded goal against while his team is on the power play. Power-play goals fo

Shown on: NHL skater profiles — column +/-

The share of shots on goal a goaltender stops. It is written as a three-digit decimal (.915) and is less dependent on team defence than goals-against average, because it divides by the shots actually faced.

Assists per 90 minutes played, the playmaking counterpart of goals per 90. StatVault's MLS assist counts are primary assists (the final pass before the goal). Rates from small minute totals are unstable.

Shown on: MLS player profiles — column A/90

The probability that a shot becomes a goal, estimated by a model fitted to large numbers of past shots using features such as distance, angle, body part and the kind of play that created the chance. A player's or team's xG is the sum of those probabilities over its shots, so goal

Goals scored per 90 minutes played — a full match — so players with different minutes can be compared on one scale. Rates from small minute totals are unstable: one goal in a 30-minute cameo is a 3.00 rate.

Shown on: MLS player profiles — column G/90