Two equations have been derived in this paper for expecting the ozone generation inside dry air fed silent discharge reactors. The derived equations have been built on theories of the silent discharges and their applications, reported in the literature. The two equations have been investigated individually with experimental results for ozone generated by silent discharges in coaxial cylindrical reactors. The reactors were stressed with an ac voltage and fed by dry air flowing with constant rates at atmospheric pressure and room temperature. The results, that have been calculated by the two equations individually, have agreed with the experimental results over the whole range of the investigated parameters. Subsequently, the two derived equations represent suitable criteria for expecting the ozone concentration generated by silent discharges in dry air fed coaxial cylindrical reactors under any discharge conditions in range of the investigated parameters.