Two explicit formulae for the effective piezoelectric coefficients (d(31) and d(33)) of 0-3 composite have been derived by taking into account the interaction effects between the inclusions and are expressed directly in terms of the properties of the constituents. Predictions using these two formulae are compared with published experimental data of 0-3 composite systems having three different polarization states: only the inclusion phase is polarized; both phases are polarized in the same direction and the two phases are polarized in opposite directions. In addition, the predictions using Wong et al.'s scheme (Wong CK, Poon YM, Shin FG (2001) J Appl Phys 90:4690) and Furukawa et al.'s model (Furukawa T, Fujino K, Fukada E (1976) Jpn J Appl Phys 15:2119) are included for comparison. For the first two cases, the results show that both our model and Wong et al.'s scheme have comparable performance. However, for the last case, our model gives more favorable predictions than theirs.