Slugging Percentage (SLG)
$$ {\displaystyle \mathrm {SLG} ={\frac {({\mathit {1B}})+(2\times {\mathit {2B}})+(3\times {\mathit {3B}})+(4\times {\mathit {HR}})}{AT\ BATS}}} $$
Total bases divided by at bats, using the formula where 1B, 2B, 3B, and HR are the number of singles, doubles, triples, and home runs. Slugging percentage (SLG) is a measure of batting productivity of a hitter.
Unlike batting average (AVG), slugging percentage gives more weight to extrabase hits such as doubles and home runs, relative to singles. Walks are specifically excluded as a plate appearance that ends in a walk is not counted as an at bat.
The name is a misnomer, as the statistic is not a percentage but a scale of measure whose computed value is a rational number in the interval [0, 4]
. A slugging percentage is always expressed as a decimal to three decimal places, and is generally spoken as if multiplied by 1,000 (a slugging percentage of .589 is spoken as "five eighty nine"). The maximum possible slugging percentage is 4.000.
Factoids

Babe Ruth holds the MLB career slugging percentage record of .690.

The single season record SLG is held by Barry Bonds who achieved a .863 SLG with the San Francisco Giants in 2001.

In 2017, the average SLG among all batters in the Majors was .426.