From BR Bullpen

Abbreviations K/BB
Type Pitching
Components strikeouts, walks

In baseball statistics, strikeout-to-walk ratio (K/BB) is a measure of a pitcher's ability to control pitches; calculated as: strikeouts divided by bases on balls. A pitcher that possesses a great K/BB ratio is usually a dominant power pitcher, such as Randy Johnson, Pedro Martínez, Curt Schilling, or Nolan Ryan. However, in 2005, Minnesota Twins starting pitcher Carlos Silva easily led the major leagues in K/BB ratio with 7.89:1, despite only striking out 71 batters over 188⅓ innings pitched; he walked only 9 batters.

The all-time major league record for the best K/bb ratio was set by Phil Hughes of the Minnesota Twins in 2014. In 209 2/3 innings, he struck out 186 batters and allowed only 16 walks, for a ratio of 11.63. The previous mark, and the standing National League record was set by Bret Saberhagen of the New York Mets in 1994: he struck out 143 and walked 13 for a ratio of 11.00. These records are for pitchers with enough innings to qualify for the ERA title, i.e. at least one inning pitched for each of their team's games played; some relief pitchers may have had higher ratios in shorter stints.

A hit by pitch is not counted statistically as a walk and therefore not counted in the strikeout-to-walk ratio. At youth levels where hit by pitches are more common, including hit by pitches may be a more useful statistic. Walks plus hits per inning pitched can also be used to compare pitchers.