Understanding the NBA: Explaining Advanced Offensive Stats and Metrics | News, Scores, Highlights, Stats, and Rumors

Calculation

(FG+0.5*3P)/FGA

Where FG=Field Goals, 3P=Three-Pointers, FGA=Field-Goal Attempts

Explanation

Field-goal percentage (FG%) was once one of the better stats for estimating shooting ability up until the popularization of effective field-goal percentage in the 1990s. 

The only difference between the two stats is that three-pointers are weighted more heavily in eFG%. Seeing as three-pointers are worth three points and two-pointers are worth two points, this makes sense.

That may be the most ridiculously obvious sentence I've ever written. 

Don't make the mistake of thinking that the multiplier in front of three-pointers should be 1.5 though. Essentially, it is in the above formula because three-pointers are counted one time in field goals and another 0.5 times on the other side of the addition sign.

So, as for the merits of effective field-goal percentage, tell me which of the following players you'd rather have:

Player A attempts 10 shots from the field, all from within the three-point arc, and drills five of them.

Player B attempts 10 shots from the field, all from outside the three-point arc, and drills five of them.

Player A, who was responsible for 10 points, has a FG% of 50 percent, just like Player B, who was responsible for 15 points, despite shooting the same number of times. However, Player A's eFG% was still 50 percent while Player B's was a much better 75 percent.    

Limitations

While I like eFG% as a stat, there is still a measure of shooting that is significantly better. If for nothing else, that's because it takes free-throw shooting into account as well, unlike eFG%. 

You'll see what that stat is pretty soon. 

Also, the penalty for missing a three-pointer is the same as the penalty for missing a two-pointer because all attempts are weighted the same. 

Example Usage

"Ray Allen is currently leading the NBA in eFG% at 63.5 percent."

How I interpret that sentence: Ray Allen's FG% of 50.2 percent is impressive enough, but once you look at his three-point shooting prowess, his eFG% is even more impressive.