Introduction As modern people attach great importance to birth control, safe period calculators have become the focus of many female friends. However, due to the complexity of the female body and changes in menstrual cycles, it is not easy to accurately predict the safe period. Therefore, how to use the 2020 safety period calculator to predict the safety period has become an urgent problem for us to solve. This is elaborated on from four aspects below. How to choose a safety period calculator There are various safety period calculations on the market