Cohen's kappa (two raters, yes/no)
Computes Cohen's kappa for two raters and a yes/no call, from the four counts of a 2x2 table.
Open the calculator → Runs in your browser. Data leaves only if you deliberately send a problem report from the interactive tool.
Example
- Both raters said yes
- 95
- First said yes, second said no
- 2
- First said no, second said yes
- 3
- Both raters said no
- 0
Result: agreement of 95% with a kappa near zero, the first kappa paradox
The tool opens with these values already filled in. Replace them with your own.
What the result means
- The formula
- Observed agreement minus the agreement chance gives from the raters own margins, divided by one minus that.
- The labels
- Below 0 worse than chance, 0 to 0.20 slight, 0.21 to 0.40 fair, 0.41 to 0.60 moderate, 0.61 to 0.80 substantial, 0.81 and above almost perfect.
- A convention
- Landis and Koch described their own divisions as arbitrary. The labels are not a standard.
- Prevalence index
- High when almost every case falls in one category, which holds kappa down however well the raters agree.
- Bias index
- High when the disagreements run in a direction rather than at random. Kappa alone cannot show that.
- Undefined
- When every case falls in one category for both raters, chance predicts complete agreement and kappa has no value.
What you enter
- Both raters said yes
- First said yes, second said no
- First said no, second said yes
- Both raters said no
How this is calculated
Cohen J. A coefficient of agreement for nominal scales. Educ Psychol Meas. 1960;20(1):37-46. Byrt T, Bishop J, Carlin JB. Bias, prevalence and kappa. J Clin Epidemiol. 1993;46(5):423-429. Landis JR, Koch GG. Biometrics. 1977;33(1):159-174. Read the source ↗
A reference and educational tool. Not medical, legal, or financial advice, and not a substitute for clinician judgment.