The Maslach Burnout Inventory (MBI) is recognized as the leading measure of burnout and validated by 35+ years of extensive research.
The MBI measures burnout as defined by the World Health Organization (WHO) and it is used in 88% of burnout research publications (Boudreau, Boudreau & Mauthe-Kaddoura, 2015).
MBI Toolkit: https://www.mindgarden.com/184-maslach-burnout-toolkit