K% and BB%
Strikeout rate (K%) and walk rate (BB%) measure how often a position player walks or strikes out per plate appearance.* They’re measured in percentage form, so it’s easy to compare between players and years.
High walk rates are good for batters because it means they’re reaching base more often, while low walk rates are bad. Strikeout rates are a bit tougher to pin down — while making outs is bad, striking out isn’t necessarily worse than any other sort of out. If a player is still getting hits, walking, and reaching base at a high rate, then they can still be a valuable offensive piece with a high strikeout rate.
*In the past, FanGraphs carried K% as K/AB. In 2011, K% was changed to K/PA.
Context:
Please note that this chart is meant as an estimate, and that league-average strikeout and walk rates vary on a year-by-year basis. To see the league-average strikeout and walk rate for every year from 1901 to the present, check the FanGraphs leaderboards.
| Rating | K% | BB% |
|---|---|---|
| Excellent | 10.0% | 15.0% |
| Great | 12.5% | 12.5% |
| Above Average | 15.0% | 10.0% |
| Average | 18.5% | 8.5% |
| Below Average | 20.0% | 7.0% |
| Poor | 25.0% | 5.5% |
| Awful | 27.5% | 4.0% |
Things to Remember:
● Power hitters tend to have high strikeout and walk rates, since they may swing and miss often, yet are pitched around by pitchers. Contact hitters are the opposite; they tend to have low strikeout and walk rates.
● The more a player strikes out, the tougher it is for them to maintain a high batting average since they are putting fewer balls in play.
Links for Further Reading:
4
I’m assuming that BB% includes the IBB. There is a good case to be made that they should be taken out. Also, there is a case that K% should be based on PA instead of AB. It all depends on what it’s being used for, of course.
Why is K% based on at bats? If two players get 700 plate appearances each, but Player A walks 200 times and K’s 200 times, he’s got a 40% K rate.
Player B walks 0 times and K’s 200 times, he’s got a 28.5% K rate.
Don’t like that!
Works both ways.
If you take those player scenarios and instead think of it as two seasons for the same player…shouldn’t there be improvement shown in K% in year two? They struck out in 200 at bats, but didn’t strike out in 500. The fact they went from 200 walks to 0 should be handled outside of K% imo.
Either way you still need to keep BB% and K/BB in view.