Macfax Four Factor Index
One standardized score from four possession-level margins
The Four Factor Index (FFI) converts the four possession-level margins into a single 0–100 score. Each margin is standardized relative to the national Division I distribution for that season, then combined using weights derived from foundational basketball research and refined empirically for college basketball. FFI exists in both raw and adjusted forms — the adjusted version accounts for opponent quality and is the primary metric displayed on Macfax.
What It Measures
FFI measures a team's composite possession-efficiency advantage across all four margins — shooting quality, ball security, offensive rebounding, and free throw rate pressure — weighted by how much each dimension historically drives team performance. A higher score means a more dominant overall possession profile. Both a raw version (from unadjusted margins) and an adjusted version (from opponent-adjusted margins) are computed. The adjusted FFI is the primary value shown on Macfax.
Why It Matters
Individual Four Factor margins require context to interpret. A +4 eFG margin is excellent; a −2 rebounding edge might not matter much if the team has elite shooting and turnover advantages. FFI removes that friction by collapsing all four margins into a single number on a consistent scale, with shooting weighted most heavily because it predicts outcomes most reliably. It is easier to compare two teams' overall possession profiles at a glance than to mentally weigh four separate margins.
How to Interpret
FFI is centered at 50, which represents exactly average national Four Factor performance for that season. Scores above 60 are strong. Scores above 80 are elite. Scores below 40 indicate structural possession-level disadvantages. The scale is capped at 0 and 100. One important caveat: FFI is season-relative. A score of 68 in 2025–26 reflects performance relative to 2025–26 Division I averages, not a universal standard. Scores are not directly comparable across different seasons.
Formula
Weighted Z-Score = w₁·z_eFG + w₂·z_TOV + w₃·z_REB + w₄·z_FTR Each z-score is computed relative to the current season's national Division I distribution.
Component Weights
| Factor | Weight |
|---|---|
| eFG% Margin | 47% |
| Turnover Edge | 24% |
| Rebounding Edge | 21% |
| Free Throw Rate Margin | 8% |
Technical Notes
- Weights were inspired by Dean Oliver's foundational Four Factors research and empirically refined for college basketball. College basketball differs from the NBA data Oliver originally analyzed, particularly in the relative importance of shooting vs. other factors.
- eFG% margin carries the highest weight because shooting quality is the single strongest predictor of possession-level success at the college level in the current version.
- Z-scores are computed relative to the full Division I national distribution for the current season. This means FFI scores shift year to year as the national baseline shifts.
- The 20× scale multiplier controls the spread of the 0–100 distribution. The exact calibration is internal to Macfax.
- Individual component z-scores (eFG, TOV, REB, FTR) are available separately to show where a team's FFI is coming from.
- Weights may be recalibrated between seasons as additional validation data accumulates.
- •FFI scores are not comparable across seasons — a 68 in 2025–26 and a 68 in 2026–27 are relative to different national baselines.
- •Two teams can have identical FFI scores through very different factor profiles. Check individual margins to understand how a team achieves their score.
- •Early-season FFI is directional only. Adjusted margins stabilize more slowly than adjusted efficiency, and the national z-score distribution is noisier with fewer games played.
- •Adjusted FFI depends on the accuracy of opponent-adjusted four factors, which carry the same schedule-imbalance limitations as adjusted efficiency ratings.
- •Weights may be recalibrated between seasons, which means a score of 65 in one season may be weighted slightly differently internally than a 65 in the prior season.
Illustrative: Team A and Team B both have FFI 64. Team A gets there through dominant shooting (+7 eFG margin, +2 TOV edge, −1 rebounding edge, +3 FTR margin). Team B gets there through elite defense and rebounding (+3 eFG margin, +4 TOV edge, +6 rebounding edge, +1 FTR margin). Both score 64 — but they are stylistically very different teams, and their profiles match up differently against specific opponents. FFI tells you the overall possession quality level; the individual margins tell you the story.