This FIP calculator computes Fielding Independent Pitching — ((13×HR) + 3×(BB + HBP) − 2×K) ÷ IP + constant — an ERA-scaled grade built only from the outcomes a pitcher controls most directly: home runs, walks, hit batsmen and strikeouts. The defense, the park’s quirks and batted-ball luck are stripped out by design.

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The Pitcher, Alone With His Three True Outcomes

FIP emerged from a discovery (Voros McCracken, 2001) that rattled baseball: pitchers have surprisingly little control over whether balls in play become hits — BABIP fluctuates around a pitcher's head largely independent of his skill. What pitchers DO control repeatably: strikeouts, walks, hit batsmen and home runs. FIP prices exactly those, weighting by run value (HR ≈ 13, free pass ≈ 3, K ≈ −2 in the formula's units) and adding a league constant (~3.10 in recent MLB seasons) to land on the ERA scale. The defaults describe a quality starter: (156 + 144 − 300)/180 + 3.10 = 3.10 FIP. The diagnostic use dominates: FIP tracks FUTURE ERA better than ERA itself, so a starter running a 4.60 ERA with a 3.40 FIP is a buy-low candidate (his defense/luck should normalize), and the 3.20 ERA / 4.40 FIP darling is a sell-high. Its known blind spots are symmetric with its virtues: ground-ball pitchers who induce weak contact get no credit (their balls in play ARE softer), knuckleballers historically beat their FIP forever, and HR/FB luck leaks into the one batted-ball category FIP does count — refinements (xFIP normalizing HR/FB, SIERA modeling contact) layer on top, all starting from this formula's skeleton.

The constant deserves its footnote: it is recalculated per league-season so that league FIP equals league ERA — 3.10 is the recent MLB neighborhood, but a 1999 or a softball constant differs; the input exists so the stat can travel across eras and levels honestly rather than borrow this decade's calibration.

Worked Examples (Verified)

  • Defaults: (13×12 + 3×48 − 2×150)/180 + 3.10 = 0/180 + 3.10 = 3.10 FIP.
  • The homer problem: same line but 30 HR: (390 + 144 − 300)/180 + 3.10 = 1.30 + 3.10 = 4.40 — home runs are FIP's loudest input, as run prevention demands.
  • The regression candidate: a reliever at ERA 5.10 whose FIP computes 3.55 has been sequencing-and-defense unlucky; front offices pay for the 3.55.

FIP Discipline

  • Use the right constant for your league/season when precision matters — FIP comparisons across constants are comparisons of constants.
  • Intentional walks: official FIP variants (FanGraphs) exclude IBB from the walk term; this page's input takes total BB — subtract IBB before entering if matching that convention.
  • Small relief samples swing on one homer (+13/IP is enormous over 8 innings): FIP needs 50+ innings to speak with confidence, like every rate here.
  • FIP is not a prediction machine by itself: age, velocity trends and injury context sit outside it — it grades the outcomes recorded, cleaner than ERA, not completely.
  • Ground-ball specialists will chronically “underperform” FIP — treat persistent multi-year ERA < FIP for extreme sinkerballers as a skill signal, not luck.
  • FIP's inventor context matters: it grades a pitcher in a NEUTRAL park/defense — moving from a pitcher-friendly park with a great defense to Coors Field with a porous one changes ERA far more than it changes FIP, and front offices budget accordingly.

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Frequently Asked Questions

How do you calculate FIP?

FIP = ((13×HR) + 3×(BB + HBP) − 2×K) ÷ IP + FIP constant. Defaults: (156 + 144 − 300)/180 + 3.10 = 3.10. The constant (~3.10 in recent MLB) aligns league FIP with league ERA; innings use baseball thirds notation, converted automatically here.

What is a good FIP?

Because it shares ERA's scale, the bands rhyme: under 3.20 excellent, 3.20–3.80 above average, ~3.90–4.20 league average (season-dependent), 4.80+ poor. The interpretation differs from ERA: FIP says what the pitcher's own outcomes deserved, so it is read as skill, while ERA is read as history.

Why does FIP ignore hits?

Because research showed pitchers control batting average on balls in play far less than anyone assumed — most of the variation is defense, park and fortune. Hits that aren't home runs are therefore excluded as noise. The one hit type retained (home runs) rarely involves the defense at all. It's a deliberate model choice, not an oversight — and the ground-ball-pitcher exception is its documented price.

FIP vs ERA — which predicts better?

FIP, consistently: year-to-year FIP correlates with next season's ERA more strongly than ERA correlates with itself. That's the regression logic — defense and sequencing luck wash out, strikeout/walk/home-run skills persist. ERA remains the record of what happened (and what standings counted); FIP is the scouting report on what the pitcher did.

What is xFIP and SIERA?

xFIP replaces actual home runs with an estimate from fly balls × league HR/FB rate, removing HR luck too; SIERA models the interactions (ground-ball rate, strikeouts) more richly. Both are refinements layered on FIP's insight, published by the major analytics sites with league constants of their own. FIP remains the hand-computable core — the one this page exists to make transparent.

Does FIP work for relievers?

Yes, with sample caution: relievers' seasons are 50–70 innings, and a single homer moves FIP by ~0.20 over 60 IP versus ~0.07 for a starter's 180. Read reliever FIP over multi-year windows, and remember leverage (when the outs happen) is a value dimension FIP deliberately ignores — a closer's 3.40 in the ninth can outweigh a long man's 3.10 in the fifth.

Where does the 3.10 constant come from?

Constant = league ERA − ((13×lgHR + 3×(lgBB + lgHBP) − 2×lgK)/lgIP), computed from league totals each season so average FIP equals average ERA. Recent MLB values hover 3.05–3.20. Other leagues/levels compute their own; entering yours in this calculator keeps cross-context comparisons honest.

Is this FIP calculator free?

Yes — free, instant, no sign-up. Enter home runs, walks, HBP, strikeouts, innings and your league constant for FIP with its context band.