Effective Field Goal Percentage — shooting percentage that credits three-pointers for being worth 50% more.
Standard field goal percentage treats every made shot identically. A made three-pointer counts the same as a made layup. That made sense in the 1960s when the three-point line didn't exist. It doesn't make sense now.
Effective field goal percentage corrects the math. It awards every made three-pointer 1.5 times the credit of a made two-pointer, matching the actual point value of the shot. A team that shoots 40% on threes is, in eFG% terms, shooting 60% — equivalent in point production to a team shooting 60% on twos.
The metric immediately changes how you read shooting profiles. A player making 45% of his shots overall with half of them coming from beyond the arc has an eFG% closer to 55% — comparable to a finisher hitting 55% of his shots on layups and dunks. Without the adjustment, the perimeter shooter looks worse than he actually is.
eFG% is the single most important factor in the Dean Oliver four-factors framework for team success. Effective shooting, turnover rate, offensive rebounding rate, and free throw rate together explain almost all of the variance in NBA team scoring efficiency. Of the four, shooting is by far the most important — typically about 40% of the explanatory weight. Modern NBA strategy, with its emphasis on three-point volume and shot selection, is essentially an eFG% optimization.
Our NBA team ratings start from offensive and defensive eFG%, adjusted for opponent. Most of the predictive power in our spread model comes from the gap between projected offensive eFG% and projected defensive eFG% allowed.