The critical distance for the Nemenyi test is calculated as:

,

where is the confidence level, is the number of models and is the number of measurements. To calculate the Studentised range statistic for infinite degrees of freedom divided by is used. The values of for up to can be download here as csv.

You may also be interested in the implementations of the Nemenyi test in MatLab and R, or a discussion on how to best visualise its results and its connection with the MCB test.