FIP Calculator Baseball

Enter the five inputs below. Hit batters are optional: leave HBP blank to run the simplified version Tom Tango published when he first developed the stat. Innings pitched accepts the standard fractional notation, where ".1" means one out and ".2" means two outs in an incomplete inning.

To calculate FIP, multiply home runs by 13, walks plus hit batters by 3, then subtract strikeouts multiplied by 2. Divide that by innings pitched and add the season FIP constant (typically 3.05 to 3.20). The result lands on the same scale as ERA, where 4.00 is league average.

FIP comes in two formula variants. Both share the same core idea (reweight HR, BB, K) but differ in whether they include hit batters and a calibrating constant.

Simple FIP (Baseball-Reference / Tom Tango)

The original formula, used in many quick-reference contexts and on Baseball-Reference's FIP page(opens in new tab), skips both HBP and the constant:

FIP = (13 x HR + 3 x BB − 2 x K) / IP

This version produces a number that is not on the ERA scale, so a "FIP" of 1.50 from this formula does not translate directly to a 1.50 ERA. It is useful for quick comparisons between pitchers but is harder to interpret in absolute terms.

Official FIP (FanGraphs)

The version FanGraphs publishes(opens in new tab) adds hit batters and a season-specific constant that pulls FIP onto the league ERA scale:

FIP = ((13 x HR) + (3 x (BB + HBP)) − (2 x K)) / IP + FIP Constant

What Each Input Does

Worked Example

A starter posts 18 HR, 45 BB, 6 HBP, 180 K over 175.2 IP (175 and 2/3, decimal value 175.67) with a FIP constant of 3.10. Plug the numbers in:

• Numerator: (13 x 18) + (3 x (45 + 6)) − (2 x 180) = 234 + 153 − 360 = 27
• Divide by IP: 27 / 175.67 = 0.154
• Add the constant: 0.154 + 3.10 = 3.25

A 3.25 FIP places this pitcher in the "great" tier on the rating scale below, indicating top-tier starter performance. If their actual ERA is 3.85, the gap signals batted-ball luck or defensive support running against them. If ERA is 2.75, FIP suggests their underlying skill matches a pitcher closer to 3.25, with some regression likely.

The FIP constant exists for one purpose: align league-average FIP with league-average ERA in a given season. Without it, the raw formula produces small numbers (like the 0.154 above) that have no intuitive meaning. The constant pulls those values into the 3.00 to 4.00 range that pitchers and coaches already use.

How the Constant Is Calculated

FanGraphs derives the constant each year from league totals using this formula:

FIP Constant = lgERA − ((13 x lgHR + 3 x (lgBB + lgHBP) − 2 x lgK) / lgIP)

The constant typically lands between 3.05 and 3.20. It moves slightly each year as the league's overall run-scoring environment shifts: in higher-offense seasons the constant rises, in lower-offense seasons it falls. The 2019 FIP constant landed near 3.21, reflecting an unusually high-scoring year, while values in lower-offense seasons sit closer to 3.10. For year-specific values such as 2022, 2023, or 2024, FanGraphs publishes the official annual figure on their Guts! constants page(opens in new tab) alongside wOBA constants and park factors.

Why You Should Match the Constant to the Year

When calculating FIP for a specific season, use that season's constant. Comparing a 2015 pitcher's FIP to a 2024 pitcher's FIP using the same constant introduces small distortions, since the run environments differ. For most coaching contexts the default 3.10 in the calculator above is close enough, but for serious season-over-season comparison, pull the year-specific constant from FanGraphs.

Default Value in the Calculator

The calculator defaults to 3.10 because it sits near the long-run historical average. If you want to calculate a pitcher's FIP for a specific year, replace the default with that year's constant from the FanGraphs Guts! page. For a quick estimate during a season in progress, 3.10 produces results that are within a few hundredths of the official figure.

A good FIP in MLB sits at or below 3.50. League average for starting pitchers tends to land between 4.00 and 4.20 depending on the run environment, so anything well below that mark indicates above-average run prevention. The benchmarks below come from FanGraphs' Sabermetrics Library(opens in new tab).

FIP Rating Scale (MLB Standard)

Career FIP Leaders and Historic Single-Season Records

The lowest single-season FIPs in MLB history come from pitchers whose strikeout-to-walk dominance was paired with extreme home-run prevention. Notable seasons that paired sub-2.00 ERA with sub-2.00 FIP include Tom Seaver (1971), Clayton Kershaw (2014), and Jacob deGrom (2018).

For a sense of sustained excellence over a career, ace-level starters typically settle into the 2.50 to 3.00 FIP range. Use these benchmarks as anchors when reading the rating scale above: most pitchers will never sit where Pedro Martinez did in 1999, but the rating tiers stay accurate for any season since.

Common FIP Questions Answered

• What is a good FIP in baseball? Below 3.50 puts a pitcher in elite or great territory. The top 10 to 15 starters in any MLB season typically post FIPs under 3.20, with Cy Young winners often landing in the 2.50 to 3.00 range when their full repertoire is working.
• Is a 4.00 FIP good? It is right around league average for an MLB starter. A 4.00 FIP is useful and rotation-worthy, but not a stat line that wins awards.
• What does a 5.00 FIP mean? A 5.00 FIP signals a pitcher is allowing baserunners and home runs at a rate that produces nearly five earned runs per nine innings on a defense-neutral basis. Most starters with sustained 5.00+ FIPs lose their rotation spot.
• Why is FIP on the ERA scale? The season-specific FIP constant pulls raw FIP values into the 3.00 to 4.00 range, matching what coaches, broadcasters, and players already use for ERA. Without the constant, FIP outputs small decimals (often under 1.00) that have no everyday meaning.
• Is FIP better than ERA? FIP is a better predictor of future performance because it removes batted-ball luck and defense. ERA is a better description of what already happened in the games a pitcher actually pitched. Most analysts use both: ERA for past results, FIP for projecting forward.
• What is the difference between FIP and xFIP? xFIP swaps a pitcher's actual home run total for the league-average home run rate per fly ball. xFIP smooths out HR variance, making it useful for forecasting next season's FIP. See the FIP variants section below for the full breakdown.

Single-Season Samples Need Context

A starter with 50 innings of work can post a FIP that swings half a run in either direction from their true talent level. FIP needs about a full season of innings (150+) before it stabilizes as a reliable signal. For relievers the sample size issue is more pronounced, which is why bullpen FIPs swing more dramatically year to year than starter FIPs.

Lower is better. FIP is on the same scale as ERA: a 2.50 FIP describes a pitcher allowing the equivalent of 2.50 earned runs per nine innings on a defense-neutral basis, and a 5.00 FIP describes the opposite. The formula itself reflects this, since strikeouts are the only input that lowers FIP (negative weight) while home runs, walks, and hit batters all raise it.

This is the same direction as ERA, WHIP, and most pitching rate stats. Hitters' stats like batting average, on-base percentage, and slugging percentage work the other way (higher is better), which is sometimes a source of confusion when first learning sabermetric stats.

Why FIP and ERA Sometimes Disagree

Two pitchers can post identical FIPs but very different ERAs over the same number of innings. The gap between FIP and ERA is one of the cleanest signals of luck or defense:

• ERA > FIP by 0.50 or more: Usually means batted-ball luck or defense is hurting the pitcher. ERA tends to fall over the rest of the season.
• ERA < FIP by 0.50 or more: Usually means batted-ball luck or defense is helping the pitcher. ERA tends to rise over the rest of the season.
• ERA and FIP within 0.20: The pitcher's results match their underlying skill closely, suggesting little regression in either direction.

ERA and FIP both report in earned runs per nine innings, but they measure different things. ERA captures every earned run a pitcher allows, including those that scored because of defensive positioning, batted-ball placement, or sequencing luck. FIP strips all of that out and asks: based only on the events the pitcher directly controlled, what should their ERA look like?

The defense-independent design comes from sabermetrician Voros McCracken's late-1990s and early-2000s research, which became the foundation of Defense Independent Pitching Statistics (DIPS) Theory and showed that pitchers had limited control over whether balls in play became hits. FIP applies that same DIPS insight to run prevention: by ignoring balls in play entirely, FIP isolates the part of pitching that the pitcher actually owns. For more on the batted-ball luck side of the same coin, see the BABIP calculator and DIPS theory breakdown.

When to Use FIP vs. ERA

• Use ERA for in-season standings, awards voting context, and any conversation where actual runs allowed is the question.
• Use FIP when projecting a pitcher's next year, evaluating trade targets, or trying to separate true talent from defensive support.
• Use both together for a complete picture. The gap between them tells you what is real and what is noise.

For the underlying ERA calculation across baseball, softball, and youth innings formats, see the ERA calculator. Pairing FIP with WHIP adds a baserunner-traffic dimension that ERA and FIP both miss.

FIP has two close relatives that show up regularly on sabermetric sites and broadcast graphics. Both refine the underlying idea in different ways.

FIP Minus (FIP-)

FIP- scales FIP to the league average and adjusts for park effects. The league average is set to 100, and every point below 100 represents one percent better than league average. A FIP- of 80 means a pitcher was 20 percent better than league average, while a FIP- of 120 means 20 percent worse.

This makes cross-era and cross-park comparisons cleaner than raw FIP, since a 3.50 FIP in a high-offense year is more impressive than a 3.50 FIP in a pitcher-friendly year. FIP- accounts for both differences in one number.

xFIP (Expected FIP)

xFIP replaces a pitcher's actual home run total with the league-average home run rate per fly ball. The idea is that home run rate per fly ball is more variable year to year than the underlying skill of inducing weak contact, so xFIP smooths out that variance.

A pitcher with an unusually high or low HR/FB rate in a given season often sees their FIP regress toward their xFIP the following year. xFIP is most useful for projecting future performance, less useful for describing what already happened. For deeper context on how rate stats interact with batted-ball luck, the BABIP guide covers the same theme on the hitter side.

FIP stabilizes faster than ERA because it removes one of the noisiest sources of variance: batted-ball outcomes. For coaches tracking pitcher development, this means FIP is a stronger forward-looking signal than ERA, especially over the first half of a season when small samples can make ERA misleading.

A starter with a 4.50 ERA and a 3.40 FIP through 60 innings is almost certainly pitching better than the ERA shows. The opposite scenario (3.40 ERA, 4.50 FIP) suggests regression is coming. Both gaps tend to close as innings accumulate, with FIP usually winning the tug-of-war.

For amateur pitchers, FIP is harder to apply directly because home run rates are inflated and league constants are not published. The underlying logic still works: a youth or high school pitcher whose strikeouts and walks look strong but whose ERA looks rough is probably a victim of weak defense. Tracking K, BB, HR, and HBP alongside ERA each outing reveals the pattern.

Platforms like Striveon let you log per-outing pitching stats, attach notes about defensive context, and watch the trends connect over a full season. Track pitcher development with Striveon's evaluation tools to pair FIP-style metrics with skill observations and outing notes. For coaches building a complete stat picture from scratch, the athlete development and management solution combines stat tracking with goal setting and progression tools.

If you record game data by hand, a baseball scorecard captures the inputs you need for FIP, WHIP, and other pitcher metrics. For the offense side, the batting average calculator covers the simpler hitter math and rating scales in detail.