Long-term deflections of reinforced concrete flexural members caused by creep and shrinkage are significantly affected by material and geometric properties such as concrete strength, member dimension, and reinforcement detail. However, current methods specified in KCI 2007, KBC 2009, and ACI 318-08 cannot accurately address the effects of these material and geometric properties. In the present study, a simplified method for the calculation of long-term curvatures due to creep and shrinkage in cracked section was developed. For simple formulation, constant stress in tensile re-bars and a triangle distribution of reduced concrete stress increment were adopted. Using the long-term curvatures, the long-term deflection of cracked flexural members was calculated by using the effective stiffness and by direct integration of long-term curvatures along the member span. The proposed method was applied to 30 beam and one-way slab specimens. The results showed that the proposed method predicted well the long-term deflections of the beam and slab specimens addressing material and geometric properties. In particular, the direct integration of long-term curvatures along the member span resulted in more reliable estimation with low scatter than the existing methods.