Field-goal percentage has one flaw big enough to change coaching decisions: it counts a three and a two as the same shot. They aren't. One pays 50 percent more.
Effective field-goal percentage fixes exactly that and nothing else. The formula gives a made three 1.5 times the credit of a made two, because that's what the scoreboard does. No possession estimates, no adjustments, no model. It's the same box score you already have, counted the way points actually accrue.
The maths that changes the argument
Run the exchange rate once and it sticks with you. A player shooting 33 percent from three produces the same points per shot as a player shooting 50 percent from two. Thirty-three from deep equals fifty inside. That one line settles most gym arguments about whether a shooter is "efficient."
Raw FG% slanders a certain kind of player. A wing taking most of her shots from the arc might sit at 38 percent overall and look ordinary in the paper's box score. Weight her threes properly and she's producing like a 50 percent two-point scorer. The reverse trap exists too: a big who never leaves the restricted area posts a shiny FG% while producing the same points per attempt as the "cold" shooter everyone wants benched.
The bench version: before you call a player inefficient, check what her shots are worth, not just how many go in.
Where it earns its keep in a scout
Reading an opponent's shooters honestly. The dangerous player is the one producing the most points per attempt, whatever her raw percentage. eFG finds the volume three-point shooter whose 34 percent is actually a problem, and exposes the mid-range specialist whose 42 percent is actually a gift to your defence.
Deciding what to concede. Every defensive scheme concedes something. eFG tells you what each concession costs. Living with a non-shooter's threes is cheap. Living with a 36-percent-from-deep guard's threes costs you more than her raw FG% suggests, because every make is half again as expensive.
Judging your own shot diet. Track your team's eFG by game and you learn whether a "bad shooting night" was cold shooting or a bad menu. Same percentage on a worse shot mix is a process problem, and process problems are fixable in the gym.
What it still doesn't count
eFG covers shots from the field and stops there. It doesn't know about free throws, so a player who lives at the line is still undersold; that's the next step up (true shooting), and it matters for foul-drawing guards. It doesn't know about turnovers, so a team can post a healthy eFG while bleeding possessions before a shot ever goes up. And like every shooting number it needs a sample before you trust it: a hot month from deep can dress up a shot diet that will regress.
None of that sends you back to raw FG%; it tells you what each number can see. FG% answers "how often do shots go in." eFG answers "what are the shots worth when they do." A coach needs the second answer far more often, and it's sitting in the same box score, one weighted line away.