 Using the molecular weight of 362.460 g/mole, the conversion factor from µg/dl to nmol/l is approximately 27.6; thus, 10 µg/dl is about 276 nmol/l.Cortisol follows a circadian rhythm and to accurately measure cortisol levels is best to test four times per day through saliva.An individual may have a normal total cortisol, but have a lower than normal level during a certain period of the day and a higher than normal level during a different period.