The type is followed by a number giving the white dwarf's surface temperature. This number is a rounded form of 50400/ T eff, where T eff is the effective surface temperature, measured in kelvins. Originally, this number was rounded to one of the digits 1 through 9, but more recently fractional values have started to be used, as well as values below 1 and above 9.(For example DA1.5 for IK Pegasi B)