Multifilamentary superconducting Nb3Sn wires are widely used for industrial applications. Wires processed by the Bronze Route technique are characterized by a large number of filaments Nb1−xSnx, with 0.18≤x≤0.25, corresponding to a distribution of Tc between<10 and 18 K. This distribution is a critical property of the wires and is important for the optimization of the conductors. However, it is not accessible to conventional techniques, due to percolation and/or magnetic shielding effects. In order to determine the Tc distribution in the sample, we have carried out specific heat measurements of various Nb3Sn multifilamentary wires (including the bronze matrix) in zero field and at 14 T. A deconvolution of the calorimetric data at the superconducting transition by means of a thermodynamical model was used for obtaining the distribution of Tc in the whole wire volume. The measurements were extended to Nb3Sn wires containing Ti additions, and the results were compared. The present calorimetric method is of primary importance for the complete characterization of Nb3Sn wires.