Removal of oxygen from feedwater is of paramount importance for safe boiler operation. Insufficient extraction of oxygen in deaeration vessels will lead to limited efficiency of oxygen scavengers and unsafe plant operation. The presented sizing procedure for packed deaeration columns is based on the similarity theory between heat and mass transfer and existing procedures. The goal of the proposed technique is not to achieve optimization of column dimensions, but to ensure that there is no undersizing of the packing height. This approach is justified considering the relatively low capital costs of deaeration columns in boiler plants. The proposed equations are based on an experimental setup involving several hundred operating regimes which have been verified and confirmed to have a high degree of accuracy.