The attractiveness of TV white space depends on the cost of secondary network. The cost mainly depends on the number of deployed cell sites. Traditionally, the required number of sites is estimated at the dimensioning stage of the network planning process. However, in TVWS the amount of available spectrum and the allowed transmission powers are not known beforehand. In this paper, the authors propose to use an iterative dimensioning process. Initially secondary cell sizes are selected based on the user density. In the cells where the capacity is not sufficient, they either reduce the cell size or increase the transmission power.