FIP Calculator — Supplied or League-Derived Constant
Calculate FIP with baseball innings notation and your chosen league constant, or derive the constant from matching league totals.
Calculate fielding independent pitching using home runs, walks, hit batters and strikeouts. Choose a matching league/season constant, or derive one from your own league totals. The default constant is only a worked-example value; the calculator does not silently treat it as a current MLB figure.
How to use this tool
- Enter the pitcher’s event counts and innings in baseball notation.
- Choose a manually supplied constant or the league-total method.
- For the league method, enter matching totals from one population and period.
- Read the weighted numerator, constant and final FIP together.
Formula
FIP = [13HR + 3(BB + HBP) − 2K] / IP + C; C = league ERA − league weighted numerator / league IP
League ERA is calculated from league earned runs and innings. This implementation uses total walks, including intentional walks, as written in the cited formula. A different convention requires a matching recalibration rather than mixing constants.
Example
With 10 HR, 20 BB, 5 HBP, 75 K and 50 IP, the weighted numerator is 130 + 75 − 150 = 55. Using the illustrative constant 3.20, FIP is 55/50 + 3.20 = 4.30.
Frequently asked questions
Where should I get the constant?
Use a documented value for the same season, league and counting convention, or enter complete league totals. A constant derived for one population need not reproduce another provider’s number.
Can FIP be negative?
Yes. The strikeout term is subtracted. The arithmetic can produce a negative value in a small or unusual sample, so the calculator preserves it instead of forcing zero.
Why can strikeouts exceed recorded outs?
A batter can reach after an uncaught third strike. The tool therefore does not impose an incorrect strikeouts-less-than-outs restriction. This does not make FIP a play-by-play scoring validator.
Sources
Last updated: 2026-10-30