Given the large inter-individual differences in performance vulnerability to fatigue that have been scientifically documented, an Individualized Fatigue Meter has potential commercial applications in industries where human performance is required 24/7, with precise operational constraints and important safety implications. Examples of this relevance include but are not limited to military operations, first responders, transportation workers, power plant operators, hospital personnel, manufacturing work forces, etc. Military operations, for example, involve sleep deprivation and circadian misalignment, particularly during sustained operations and/or when multiple time zones are crossed during deployment. The Army has an estimated 238,000 soldiers deployed overseas in 120 countries (source: US Army) coordinating to provide continuous global 24-7 operations. An individualized fatigue meter has the potential to provide biologically optimized work schedules and recommendations for fatigue countermeasures such as power naps, caffeine, light exposure, that will increase safety and the likelihood of successful operations.