Computational fluid dynamics (CFD) was used in a study of the air flow characteristics in the occupied building zone. Correlation equations between the mean air speeds and the percentage dissatisfied with the macroscopic flow numbers were derived. Ten macroscopic flow numbers including the total ventilation rate, the air change rate, ventilation rate, air diffusion performance index, modified jet momentum number, two new flow numbers and three expressions of jet momentum ratio were investigated. A total number of 25 numerical experiments under isothermal flow conditions with four different geometrical arrangements (labelled A–D) were performed. The correlation equations derived from CFD were compared with those obtained from experimental studies. It is found that the jet momentum ratio RM2 gives the equation with the best correlation coefficient and so is recommended for ventilation design.