Determining the reverberation time RT60 is a well known acoustical parameter used by acousticians to characterize acoustically a room. This paper discusses the differences in the results obtained from measuring RT60 using common standards methods defined by ASTM and ISO. It also compares and contrasts those results with acoustical modeling software (EASE) for a small office room, a gymnasium, and a small church sanctuary. A discussion between the procedures utilized, which includes type and location of sound source, position and requirements of the measurement microphones, repeatability of the measurement sample, signal used for the measurement, and frequency range, are attempted in order to evaluate common ground and a relative best practice.