BB/9 is nine times a pitcher's walks divided by innings pitched. Innings written as 209.2 mean 209 and two-thirds, not 209.2. Greg Maddux walked 23 batters in 209.2 innings in 1995: 9 × 23 ÷ 209.667 = 0.99 walks per nine innings, one of the lowest rates of the modern era.
Scouts, fantasy players and coaches use BB/9 to judge command: how often a pitcher hands a free base to the hitter, scaled to a full nine-inning game so a reliever and a starter can be compared. Enter walks, full innings and the extra outs from the stat line, and the tool converts the innings to true thirds, returns BB/9 to two decimals, and places it against rough MLB control bands, along with walks per inning and innings per walk. The working is shown line by line. One limit: the bands describe modern major-league norms, where the league rate usually sits a little above three; youth, high school and college levels walk more batters, so read the label loosely there.
Type total bases on balls for the span you want, intentional walks included.
Use the whole-number part of innings pitched, for example 209 from 209.2.
Use the stepper for the digit after the dot: 0, 1 or 2 outs.
BB/9 appears with a control band, walks per inning and innings per walk.
Result Walks per nine innings (BB/9): 0.99
Control benchmark: Elite control (under 2.00)
Innings as a decimal: 209.667
Walks per inning: 0.11
Innings per walk: 9.12
209.2 innings is 209⅔, so 9 × 23 ÷ 209.667 = 0.99 — fewer than one walk per full game across a Cy Young season.
Result Walks per nine innings (BB/9): 6.14
Control benchmark: Wild (5.00 or higher)
Innings as a decimal: 299
Walks per inning: 0.682
Innings per walk: 1.47
9 × 204 ÷ 299 = 6.14. Ryan paired that walk rate with 341 strikeouts, which is why BB/9 alone never rates a pitcher.
Result Walks per nine innings (BB/9): 4.50
Control benchmark: Below average (4.00–4.99)
Innings as a decimal: 18
Walks per inning: 0.5
Innings per walk: 2
9 × 9 ÷ 18 = 4.50, but 18 innings is short enough that two walks either way shifts the rate by a full point.
BB/9 = 9 × BB ÷ IP, where IP = full innings + outs ÷ 3
BBIP9Box scores record innings in outs, so .1 and .2 are one and two thirds of an inning. The tool first rebuilds innings from the total outs recorded, then divides walks by that figure and multiplies by nine. Using 209.2 as a plain decimal would understate innings by about 0.47 and push BB/9 slightly up; on small samples the error is larger.
In recent MLB seasons the league rate has sat roughly between 3.0 and 3.5. Below 2.00 marks elite control, 2.00 to 2.99 is good, and 4.00 or more is a concern for most starters. Hard throwers with high strikeout totals can live with a higher figure.
Standard BB/9 on sites such as Baseball-Reference counts all walks, intentional ones included. Some analysts strip intentional walks to isolate command; if you want that version, subtract them from the walk total before entering it.
Innings are tracked by outs. The .2 means two outs, which is two-thirds of an inning, so 209.2 is 209.667 innings. The tool takes the outs separately to avoid that conversion error.
BB/9 divides walks by innings, while BB% divides walks by batters faced. A pitcher who allows many hits faces more batters per inning, which inflates BB/9 even with the same walk tendency, so many analysts prefer BB% for comparing control.
No. A hit-by-pitch is recorded separately as HBP. It still puts a runner on base, so it appears in WHIP-adjacent and FIP-style metrics, but not in the walk total used here.
The figure is still walks per nine innings, so it stays comparable with other pitchers. For a per-game feel in a seven-inning league, multiply walks per inning by seven instead.
Using this tool in an assignment, article or report? Copy a citation, or a link for your website.
Tools Directory Editorial Team. (2026, October 15). BB/9 Calculator. Tools Directory. Retrieved October 26, 2026, from https://tools.milunir.com/sports/sports-performance/bb9-calculator/
Tools Directory Editorial Team. “BB/9 Calculator.” Tools Directory, 15 Oct. 2026, https://tools.milunir.com/sports/sports-performance/bb9-calculator/. Accessed 26 Oct. 2026.
Tools Directory Editorial Team. “BB/9 Calculator.” Tools Directory. Last modified October 15, 2026. Accessed October 26, 2026. https://tools.milunir.com/sports/sports-performance/bb9-calculator/.
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