We have examined temperature changes of the light refraction, birefringence, dielectric permittivity, and dielectric hysteresis loops in Sr1 – xCaxTiO3 single crystals with x = 0.014 (SCT-1.4). The dielectric properties of Sr1 – xCaxTiO3 with x = 0.007 (SCT-0.7) have been studied. We have performed ab initio calculations of equilibrium structures and total energies for three low-temperature phases of SrTiO3 and CaTiO3, based on which we have determined an expected symmetry of the ground state of their solid solution and spontaneous polarization directions in a calcium-induced ferroelectric phase in Sr1 – xCaxTiO3. In SCT-1.4, we have separated a spontaneous contribution to the light refraction, which arises due to the spontaneous electrooptical effect caused by the spontaneous polarization and its fluctuations. From the spontaneous contribution to the light refraction, based on a previously developed our phenological approach, we have quantitatively determined for the first time the values and temperature dependences of root-mean-square fluctuations of the order parameter—the polarization Psh = 〈Pfl2 〉1/2(short-range, local polar order) in the ferroelectric phase. From optical and dielectric measurements in SCT-1.4, the average value of spontaneous polarization Ps (the contribution from the long-range order) has been determined. We have estimated the values of Psh and Ps, which characterize the short- and long-range orders in the ferroelectric phase of SCT-0.7. Separate determination of the values and temperature dependences of Ps and Psh (which considerably exceeds the value of Ps in the ordered phase) has allowed us to reveal on a quantitative level new particular features of the formation of the induced polar phase in Sr1 – xCaxTiO3.