Ceramic perovskite material with the chemical formula $Ba_{1-x}Ca_xTiO_3$ (where $x = 0.1, 0.2, 0.3, 0.4, 0.5$ and $0.6$) was prepared by using solid-state reaction technique for preparation of ceramic materials. X-ray diffraction results were compared with the international center for diffraction data (ICDD). Rietveld refinement using FullProf and Unit Cell programs was carried out and it was found that the structural phases of the samples with $x = 0.1$ and $0.2$ are tetragonal belonging to $P4mm$ space group. The sample with $x = 0.3$ possesses biphasic structure (tetragonal and orthorhombic) having $P4mm$ and $Pmmm$ space groups respectively, whereas the samples with $x = 0.4, 0.5$ and $0.6$ have orthorhombic structure with $Pmmm$ space group. Lattice parameters, unit cell volume, X-ray density and crystallite size for the diffraction peak (110) have been calculated for all samples and the results show the effect of Ca substitutions on the structural properties of $BaTiO_3$ ceramic perovskite. By using Powder Cell program and the refinement information, the unit cell and the crystal structure have been plotted for the sample with $x = 0.1$.