Herein, ab initio calculations of the electron density of states (DOS) of sodium-bismuth titanate ${\text{Na}}_{0.5}{\text{Bi}}_{0.5}{\text{TiO}}_3$, potassium-bismuth titanate ${\mathrm{K}}_{0.5}{\text{Bi}}_{0.5}{\text{TiO}}_3$, lead titanate ${\text{PbTiO}}_3$ and some of their solid solutions are presented. The DOS is calculated and compared with available data, respectively. For all compositions, an energy gap of about 1.6 eV is obtained. The theoretical results show an increasing value of the bulk modulus when the lead titanate contents of potassium-bismuth titanate and sodium-bismuth titanate are increased.