Systems, methods and apparatus are provided through which in some implementations a non-contact thermometer determines a body core temperature of a subject from electromagnetic energy of a forehead source point of a subject by a microprocessor or printed circuit board, wherein determining the body temperature of the subject includes calculating the body core temperature in reference to a numerical representation of the electromagnetic energy of the forehead source point, a mathematical formula of an ambient temperature reading, an ambient air temperature reading, a representation of a calibration difference and a bias in consideration of the forehead source point.
