Abstract: An automated gas permeameter measures permeabilities of porous samples, such as rocks, ranging from 0.1 milliDarcys to 10 Darcys within 0.5% under dry and humid conditions. The automated gas permeameter includes a program for estimating a coarse permeablity value. The program uses the coarse value to determine settling time for pressure to reach steady state within 0.1% and optimal operating conditions, such as the setting of mass flow rates imposed on the sample. Operating conditions of the permeameter are set by the program according to the resolution and range of flow controllers, accuracy of a pressure transducer, and the limit of applicability of Darcy's law for a sample.