Radon (222Rn), being a radioactive gas has its parent nucleus originated from 238U. From 238U there is a series of 14 decays to form a stable nucleus of 206Pb. The equilibrium factor in its simple term may be defined as ratio of the amount of progeny nucleus to that of a parent nucleus. Measurement of Equilibrium Factor (F-factor) for radon has been carried out in 24 dwellings in Aizawl City, which were specifically selected according to the site location and materials used for construction of the dwellings. In measuring F-factor for radon we have made use of absorber-mounted nuclear track detectors (LR-115) which selectively register the tracks due to alpha emissions from 214Po which is the 222Rn progeny species. This detector is termed as DRPS (direct radon progeny sensor). DRPS is used for estimating the Equilibrium Equivalent Radon Concentration (EERC). The concentration of 222Rn is measured by using Solid State Nuclear Track Detector (LR-115) mounted in a BARC type twin cup dosimeter. The F-factor for radon is then calculated using the measured EERC and measured concentrations of radon. Our measurement shows the F-factor for radon in Aizawl city is 0.3, which is close to the worldwide value (0.4) for indoor conditions.