Reference
Metric Library
Every stat, projection input, and concept used on the site — definition, formula, why it matters. Cite this page from any column header you don't recognize.
| Term | Definition |
|---|---|
| wOBA | Weighted On-Base Average. Linear-weights formula assigning run value to each offensive event: BB=0.69, HBP=0.72, 1B=0.89, 2B=1.27, 3B=1.62, HR=2.10. Divided by PA−IBB. Best single-stat summary of offensive value. League avg ~.315; .400+ is MVP-tier. |
| wRC+ | 100 × (player wOBA / league wOBA), park-adjusted. 100 = league average; 150 = 50% better than average; 80 = 20% below. Park-and-league-adjusted offensive index. Easier to read than wOBA. |
| WAR | Wins Above Replacement. Composed of BAT (wOBA-derived runs vs avg) + RUN (SB/CS + UBR) + FLD (defensive runs) + POS (positional adjustment) + REP (replacement-level credit), divided by Runs Per Win (RPW=9.8). Single-number player value metric. 5+ WAR = All-Star; 8+ = MVP-tier. |
| FIP | Fielding Independent Pitching. (13×HR + 3×BB − 2×K)/IP + constant. Strips out defense + luck, focuses on what a pitcher controls (Ks, walks, HRs). Better year-over-year predictor than ERA. Lower = better. League avg ~4.20. |
| FIP+ | League ERA / player FIP × 100. 100 = league avg, 150 = elite, 80 = below. Park/league-adjusted pitching index. Mirror of wRC+ for pitchers. |
| ERA+ | League ERA / player ERA × 100, park-adjusted. Higher is better. Traditional pitcher rate normalized to league + park. |
| BABIP | Batting Average on Balls In Play. (H − HR) / (AB − K − HR + SF). Strips HRs and Ks. League avg ~.291. Year-over-year correlation only ~0.4 — heavily luck-influenced for hitters; more skill-driven for pitchers. |
| ISO | Isolated Power. SLG − AVG. Pure extra-base hit rate. League avg ~.155. Power-only metric; .250+ = elite slugger. |
| K% | Strikeouts / Plate Appearances. League avg ~22%. Lower for hitters = better contact; higher for pitchers = better stuff. |
| BB% | Walks / Plate Appearances. League avg ~8.5%. Higher for hitters = better discipline; lower for pitchers = better command. |
| MLE | Minor League Equivalency. Per-stat translation factor scaling MiLB rates to MLB-equivalent: AAA K% × 0.88, AA × 0.81, A+ × 0.77, A × 0.74, ROK × 0.68 (pitcher example). Lets us compare MiLB performance to MLB on the same scale. |
| Conf% | Trade-value market confidence. Discount factor (55-100%) applied to projected value: 55% for pure prospects (no MLB exposure), 65% debut-year, 78% full-season, 90% established, 100% proven (3000+ MLB PA). Reflects bust risk for unproven players. Per FanGraphs Trade Value methodology. |
| Marcel | Forecasting method weighting prior 3 seasons (5/4/3 for hitters, 6/3/1 for pitchers) with regression toward mean. Each season's BF/PA discounted by per-level reliability. |
| Aging Curve | Per-stat year-over-year delta derived from historical paired-season data. R168: survivorship-corrected with imputed dropout pairs (cut players assigned synthetic replacement-level seasons). |
| Statcast | MLB's high-tracking data. Exit velocity, launch angle, sprint speed, fastball velo, etc. Used to derive xwOBA / xBA / barrel% / whiff% percentile bars on player pages. |
| UBR | Ultimate Base Running. Non-SB baserunning value (taking extra bases, avoiding outs). Component of WAR's RUN bucket. |
| CFraming | FanGraphs catcher framing runs. Strikes added/lost vs league-average framer. Year-over-year correlation ~0.65 (more stable than other catcher metrics). |
| Replacement Level | Performance level of a freely available minor-league call-up. Hitter ≈ 0.275 wOBA (≈ -20 wRAA/600 PA). Pitcher: SP FIP 5.30, RP FIP 4.95. |
| RPW | Runs Per Win. Conversion factor between run differential and wins. OGILVIE uses 9.8 (calibrated to 2024-25 run env ~4.38 R/G). |
| OFP | Overall Future Potential. 20-80 scout grade summarizing a prospect's projected ceiling. 50 = MLB regular; 60 = above-average starter; 70 = All-Star; 80 = HOF-tier. |
| FV | Future Value. Same as OFP. Used by FanGraphs The Board. |
| ROS | Rest Of Season. Projection for what's left of the current MLB season. Combined with YTD actual = season-end estimate. |
| ROS_FRAC | Fraction of season remaining. As of build time = days_remaining / 185 (full season). Used to scale full-season projections to season-end estimates. |
| CBT | Competitive Balance Tax (luxury tax). Soft payroll cap. 2026 base ~$238M; teams over pay tax on overage. OGILVIE uses CBT × 1.04^year as 'budget cap' for FA Room calc. |
| NPV | Net Present Value. Deferred salary discounted to today's dollars. Ohtani $680M deferred → ~57.5% NPV (1 - 0.85 × 0.50). |
| Super-2 | Top 22% of arb-eligible players by service time get a 4th arbitration year (Arb-0). Detected via debut-year heuristic. Lower share (25% of FA value) than standard Arb-1 (41%). |
| Arb-1/2/3 | Years 4/5/6 of MLB service. Salary set by arbitration hearings. Industry shares of FA AAV: 41%/62%/82%. |
| PA | Plate Appearances. Counting stat for hitters. |
| BF | Batters Faced. Counting stat for pitchers (PA equivalent). |
| TBF/G | Total Batters Faced per Game. Workload-per-appearance signature: SP starters ~26-29; openers ~12-18; closers ~4-5. Used as a comp-matching feature for pitchers (R171). |