Batting Average (AVG)
Hits divided by at-bats. A .300 hitter is excellent; .250 is roughly league average; below .220 is a struggle. AVG is the oldest hitting stat, but it treats a single and a home run identically and ignores walks entirely.
On-Base Percentage (OBP)
How often a hitter reaches base per plate appearance — hits, walks, and hit-by-pitches all count. An OBP of .370 is very good; .320 is average. Because not making an out is the single most valuable thing a hitter can do, OBP correlates with scoring far better than AVG.
Slugging Percentage (SLG)
Total bases divided by at-bats. A single is one base, a double two, a triple three, a home run four. SLG measures power. A .500 SLG is strong; the league sits around .400.
OPS — The Quick Combination
OPS adds OBP and SLG into a single number that captures both getting on base and hitting for power. An .850 OPS is a clear above-average hitter; .700 is below average; 1.000 is elite. It is the fastest honest summary of a hitter you can get from the back of a card.