Assessing the performance level of each trail runner, the UTMB Index is calculated for each of the 4 UTMB World Series race categories: 20K,50K,100k and 100M. Trail runners are also given a General UTMB Index calculated by combining results from all race categories.

Mandatory to enter the UTMB Mont-Blanc lottery, a valid UTMB Index is achieved by completing at least one race of the UTMB World Series or a UTMB Index race in the relevant category within the previous 24 months.