Multiferrroic Bi1-xCaxFe1-xMnxO3 (x=0.15) is prepared by auto combustion method using glycine as a fuel. The effect of co-substitution of Ca and Mn on structural properties of bismuth ferrite ceramics was studied. The prepared samples are analyzed by XRD and FTIR studies. The crystallite development in the BCFMO is investigated by X-ray peak broadening methods like Williamson Hall (W-H) plot, Scherrer method and Size -Strain plot method. A well defined perovskite phase with tetragonal system is observed from the XRD data. The results showed that the mean crystallite size of the BCFMO estimated from the different methods are highly inter correlated. The Rietveld refinement of XRD pattern shows that it belong to rhombohedral R3C space group. It also confirms that substitution of Ca2+ and Mn3+ creates oxygen vacancies in the system that in turn suppresses the displacement of Bi3+ ions from its centrosymmetric position and also the distortion. The FTIR studies carried out on these samples shows peaks correspond ing to 554 cm-1 which confirms the formation of metal oxide bonds and hence the formation of BFO.