A method for the measurement of the longitudinal piezoelectric coefficient d33 of single ceramic fibres with diameters 100?500 µm was recently developed. The voltage was applied using annular electrodes and the resulting displacement was measured by a capacitive method. In this paper, a number of calculations regarding the field distribution and the resulting piezoelectric displacement are presented for a typical lead zirconate titanate (PZT) ceramic. Provided that the fibres are ideally poled in the longitudinal direction, they can be modelled using the finite element method taking into account linear constitutive equations. The deviation of the measured and the actual d33 was modelled for a broad range of heights and diameters of the fibres and different electrode dimensions. The electric field distribution was analysed for typical examples and the influence of the mechanical stress on the measured d33 was studied. For sufficiently long and thin fibres the field distribution of the electric field is quite uniform and the d33 can be measured with high accuracy. Moreover, it was shown that for such fibres the measured piezoelectric coefficient d33 is determined by no other material parameter of the ceramics. The found trends of preferable geometries for the measurement can apparently be transferred to other piezoceramics.