Mental calculation is an important competence in everyday life, and it is essential especially for a future primary school teacher. In this research the efficacy of different games, as didactic games, board-games, and mobile games for developing mental calculation skills were studied. The results shows that didactic games and board-games were efficient in developing mental calculation skills when the operations are presented visually, and the didactic games and mobile games, when the operations are presented orally. In case of visually presented operations there is no statistically significant difference between the effects of the three type of games. In case of orally presented operation the didactic games had a significantly higher effect on developing mental calculation skills as the other two type of games.