FIP Calculator (Baseball)

FIP is a statistic that measures a pitcher's performance based only on outcomes they can directly control: home runs allowed, walks, hit batters, and strikeouts. It strips out the influence of defense, luck, and batted ball sequencing. The result is scaled to look like ERA, making it easy to interpret alongside traditional statistics.

The formula is: FIP = ((13 × HR) + (3 × (BB + HBP)) − (2 × SO)) / IP + FIP Constant. Home runs are weighted most heavily (×13) because they are the most damaging outcome; walks and hit batters add runs (×3); and strikeouts reduce runs (×2). The FIP constant adjusts the scale to match league ERA.

The FIP constant normalizes FIP to the ERA scale so the two stats are directly comparable. It equals lgERA − ((13 × lgHR) + (3 × (lgBB + lgHBP)) − (2 × lgSO)) / lgIP, where 'lg' denotes league-wide totals. For MLB it typically sits around 3.10, though it shifts slightly year to year.

FIP is interpreted similarly to ERA. An FIP below 3.00 is considered excellent (All-Star / elite level), 3.00–3.75 is above average, 3.75–4.20 is average, 4.20–5.00 is below average, and above 5.00 is poor. Context matters — league environment and ballpark factors can shift expectations.

ERA is affected by factors outside a pitcher's control, such as how well fielders convert balls in play into outs and whether inherited runners score. FIP isolates only strikeouts, walks, hit batters, and home runs — events research shows correlate strongly with pitcher skill across seasons — making it a more predictive indicator of future performance.

If FIP is significantly lower than ERA, the pitcher likely suffered from poor defense, bad luck on balls in play, or poor timing (e.g. clusters of hits). Their underlying skills were better than the ERA suggests, and performance may improve going forward. Conversely, a FIP much higher than ERA could signal a pitcher who has been 'lucky' and may see ERA rise.

Enter innings pitched as a decimal. Each out is one-third of an inning, so 6 innings and 1 out = 6.333, 6 innings and 2 outs = 6.667. Some scorebooks record partial innings with a .1 or .2 notation — make sure to convert that to the correct decimal (e.g. 145.1 IP = 145.333) before entering it here.

Pedro Martínez's 1999 season is widely cited as one of the lowest FIPs in modern MLB history, with a FIP around 1.39, reflecting his extraordinary strikeout rate and minuscule home run and walk totals over a full season. Historical records vary slightly depending on the FIP constant used for that era.