Two players both hit .250. One walks constantly and is always on base; the other almost never walks. Batting average calls them identical. On-base percentage doesn't — and that's the whole point.
Batting average only counts hits. On-base percentage (OBP) also credits walks and hit-by-pitch — it measures how often a player reaches base *by any means*.
The formula: OBP = (hits + walks + hit-by-pitch) ÷ (at-bats + walks + hit-by-pitch + sacrifice flies). You don't need to memorize it — but you do need to know that a walk helps OBP and does nothing for average.
Runs start with base-runners. A hitter who gets on base 40% of the time creates far more scoring chances than one who gets on 30% of the time, even if their batting averages look similar. Getting on base is the job.
If a player's average is flat but their OBP is climbing, they're learning the strike zone — laying off bad pitches and drawing walks. That's real progress that batting average alone would hide. Track walks (see what stats to track) and you'll catch it.
Many coaches value it more, because reaching base — by hit or walk — is what creates runs. Both are useful; OBP just captures more of what makes a productive hitter.
For reference, an OBP above about .400 is excellent in Major League Baseball. For youth players, watch whether it's trending up over the season rather than chasing a fixed number.