xFIP Calculator (Expected FIP)
Our baseball calculator computes fip expected fip instantly. Get accurate stats with historical comparisons and benchmarks.
xFIP Calculator (Expected FIP)
Calculator
Adjust values & calculateEnter your values below. Every result is computed in your browser — no data is sent to any server.
Formula: xFIP = ((13 * Expected HR) + (3 * (BB + HBP)) - (2 * K)) / IP + FIP Constant
Worked example — FIP: 2.79 | xFIP: 2.85 | Actual HR/FB: 10.0% | Expected HR: 18.9
Formula
xFIP = ((13 * Expected HR) + (3 * (BB + HBP)) - (2 * K)) / IP + FIP Constant
Where Expected HR = Fly Balls * League HR/FB Rate, BB = Walks, HBP = Hit by Pitch, K = Strikeouts, IP = Innings Pitched, and FIP Constant is approximately 3.10 (calibrated so league FIP = league ERA).
Worked Examples
Example 1: Ace Pitcher Season Analysis
Problem:A starting pitcher has 200 IP, 220 K, 45 BB, 3 HBP, 180 fly balls, 18 HR allowed. League HR/FB is 10.5%. Calculate FIP and xFIP.
Solution:FIP = ((13*18) + (3*(45+3)) - (2*220)) / 200 + 3.10 FIP = (234 + 144 - 440) / 200 + 3.10 = -62/200 + 3.10 = -0.31 + 3.10 = 2.79 Expected HR = 180 * 0.105 = 18.9 xFIP = ((13*18.9) + (3*48) - (2*220)) / 200 + 3.10 xFIP = (245.7 + 144 - 440) / 200 + 3.10 = -50.3/200 + 3.10 = 2.85
Result:FIP: 2.79 | xFIP: 2.85 | Actual HR/FB: 10.0% | Expected HR: 18.9
Example 2: Unlucky Pitcher with High HR/FB
Problem:A pitcher has 150 IP, 130 K, 55 BB, 6 HBP, 160 fly balls, 28 HR allowed. League HR/FB is 10.5%. Is the HR rate sustainable?
Solution:HR/FB rate = 28/160 = 17.5% (well above league average 10.5%) FIP = ((13*28) + (3*(55+6)) - (2*130)) / 150 + 3.10 FIP = (364 + 183 - 260) / 150 + 3.10 = 287/150 + 3.10 = 5.01 Expected HR = 160 * 0.105 = 16.8 xFIP = ((13*16.8) + (3*61) - (2*130)) / 150 + 3.10 xFIP = (218.4 + 183 - 260) / 150 + 3.10 = 141.4/150 + 3.10 = 4.04
Result:FIP: 5.01 | xFIP: 4.04 | HR/FB 17.5% likely to regress toward 10.5%
Frequently Asked Questions
What is xFIP and how does it differ from FIP?
xFIP stands for Expected Fielding Independent Pitching and is a refinement of the FIP (Fielding Independent Pitching) statistic. While FIP uses a pitcher's actual home runs allowed, xFIP replaces the actual home run total with an expected number based on the league-average home run per fly ball rate. This adjustment is made because research has shown that pitchers have limited control over the percentage of their fly balls that become home runs. A pitcher who allows a high HR/FB rate in one season is likely experiencing bad luck and will regress toward the league average. xFIP therefore provides a more stable and predictive measure of pitcher performance than standard FIP.
How is xFIP calculated step by step?
xFIP is calculated using the same formula structure as FIP, but with expected home runs instead of actual home runs. First, calculate expected home runs: Expected HR = Fly Balls * League Average HR/FB Rate (typically around 10-11%). Then plug into the FIP formula: xFIP = ((13 * Expected HR) + (3 * (BB + HBP)) - (2 * K)) / IP + FIP Constant. The FIP constant is typically around 3.10 and is calibrated each season so that league-average FIP equals league-average ERA. The weighting of 13 for home runs, 3 for walks and hit batters, and 2 for strikeouts reflects the run value of each event in actual MLB games.
What is a good xFIP for a pitcher?
In Major League Baseball, xFIP values are interpreted similarly to ERA but tend to be more tightly clustered since they remove variance from home run luck. An elite pitcher typically has an xFIP below 3.00, which places them among the top tier of starting pitchers. A very good xFIP falls between 3.00 and 3.50. League average xFIP is generally around 3.80 to 4.20, depending on the era and run environment. An xFIP above 4.50 suggests below-average performance, while values above 5.00 indicate significant struggles. Relief pitchers tend to have lower xFIPs due to shorter outings and higher strikeout rates, so context matters when interpreting the number.
Why is HR/FB rate important for understanding xFIP?
The home run per fly ball rate (HR/FB%) is the key variable that distinguishes xFIP from FIP. League-average HR/FB rate typically hovers around 10-11% in modern baseball. Research has consistently shown that individual pitcher HR/FB rates fluctuate significantly from year to year and that most pitchers regress strongly toward the league average over time. A pitcher with a 15% HR/FB rate one season is very likely to see that rate drop the following year, and vice versa for a pitcher with a 7% rate. By normalizing HR/FB to the league average, xFIP removes this volatile component and provides a more reliable projection of future performance than raw FIP or ERA.
What are the limitations of xFIP as a pitching metric?
While xFIP is a valuable metric, it has important limitations. First, some pitchers genuinely do have sustained ability to suppress home runs through pitch type, velocity, and movement characteristics, meaning xFIP may undervalue them. Ground ball pitchers, for example, may consistently post below-average HR/FB rates because they induce weaker fly balls. Second, xFIP does not account for batted ball quality, sequencing, or baserunner management. Third, it ignores defense-dependent events like hits on balls in play. Fourth, the FIP constant changes each season, making cross-era comparisons less reliable. Despite these caveats, xFIP remains one of the best single-number predictors of future pitcher ERA performance.
What is the FIP constant and why does the formula need one?
The bracketed expression of home runs, walks and strikeouts produces a number on no meaningful scale, so a constant is added to shift the result onto the familiar earned-run-average scale. It is derived each season as the league ERA minus the league-wide value of that same expression, which forces league-average FIP to equal league-average ERA. xFIP Calculator (Expected FIP) uses roughly 3.10, close to typical modern values. Because the constant is season-specific, comparing a FIP from one era against another without recalibrating quietly imports the run environment.
Why are the weights 13, 3 and minus 2?
They are linear weights, approximations of how many runs each event is worth relative to an average plate appearance, already scaled so that dividing by innings pitched produces a per-nine-innings figure. A home run at 13 works out to about 1.44 runs per nine innings per home run, a walk or hit batsman at 3 to roughly 0.33, and a strikeout at minus 2 to roughly minus 0.22. The ratios are what matter: a home run costs a pitcher about four times what a walk does, and about six times what a strikeout saves.
Does xFIP unfairly penalise ground-ball pitchers?
Not in the way the criticism usually assumes. xFIP normalises only the rate at which fly balls become home runs, not the number of fly balls allowed, so a sinkerballer who induces grounders keeps his fly-ball count low, his expected home run total falls with it, and the ground-ball skill itself is fully credited. What xFIP does take away is credit for keeping the fly balls he does allow inside the park, a far less repeatable skill, though a minority of pitchers appear to hold it season after season.
When should I trust FIP rather than xFIP?
Prefer FIP when there is a documented physical reason a pitcher suppresses or allows home runs beyond chance: extreme vertical movement, a home park with a distinctive fence profile, or a multi-season HR/FB rate that stays consistently off league average rather than bouncing around it. Prefer xFIP when the sample is short, when a pitcher changed parks, or when you are forecasting next season rather than describing this one. In practice analysts read FIP, xFIP and the gap between them together instead of picking one.
Why does xFIP settle down faster than ERA over a season?
xFIP is built almost entirely from strikeouts and walks, outcomes decided between pitcher and batter with no fielders, no sequencing and no scorer's judgement involved. Those rates converge on a pitcher's true talent after relatively few batters faced. ERA depends additionally on batting average on balls in play, the timing of hits, bullpen support for inherited runners and defensive quality, all of which stay noisy for months. That is why a large gap between a pitcher's ERA and his xFIP early in a season usually closes from the ERA side.
References
Reviewed for accuracy by Sher, Sports Science & Nutrition Specialist · Editorial policy
Related Calculators
🧮Expected Assists (x A)
Calculate expected assists (x a) with inputs, formulas, and instant results.
🧮Expected Goals (x G)
Calculate expected goals (x g) with inputs, formulas, and instant results.
🧮FIP Calculator (Fielding Independent)
Calculate fip (fielding independent pitching) with inputs, formulas, and instant results.
🧮Expected Goals (xG) Hockey Calculator
Calculate expected goals (hockey) (for contrast) with inputs, formulas, and instant results.
🧮X G Differential
Calculate x g differential with inputs, formulas, and instant results.
🧮Expected Goals (hockey)
Calculate expected goals (hockey) with inputs, formulas, and instant results.
🧮Sparring Load Calculator (RPE × Time)
Calculate sparring load (rpe x time) with inputs, formulas, and instant results.
🧮Soccer Expected Goals Calculator
Estimate expected goals (xG) from shot location, angle, and assist type.