In the practice of proportioning concrete compositions, the optimum sand content in a mixture of aggregates is usually found empirically. The disadvantage of this approach is the considerable complexity and duration of the required tests. The aim of the work is to develop a calculation methodology for finding the content of sand in the normal-weight concrete, taking into account the optimality criteria given. Based on the well-known theoretical concepts, the design equations are substantiated for finding the content of sand in a mixture of concrete aggregates, which ensures the lowest viscosity of the concrete mixture and prevent water separation. Using the experimental-statistical model, a method is also proposed for finding the sand content in concrete that provides the required volume of entrained air. The proposed calculation methods are confirmed experimentally.