Barium titanate (BaTiO₃) is a representative ferroelectric material, used in capacitors and electronic components such as pyroelectrics and piezoelectrics. Barium titanate exists as tetragonal and cubic systems at room temperature. The mass fractions of these two phases affect its permittivity. In addition, the c/a ratio of the tetragonal phase also affects permittivity. Therefore, it is important to determine the mass fractions of the polymorphs and lattice constants to control the permittivity of barium titanate. Rietveld analysis allows you to easily calculate mass fractions and lattice constants based on the X-ray diffraction pattern. In this example, the X-ray diffraction pattern was obtained using a compact X-ray diffractometer, equipped with the high-resolution and high-speed one-dimensional detector D/teX Ultra250. We evaluated mass fractions and lattice constants of barium titanate by Rietveld analysis.