The effective damage detection does not only require the location of damage but also the size. When a point or circular damage expands in size under stress state, it becomes thin and elongated to transform into a thin rectangular or elliptical slot. The methods introduced in this research use piezoelectric transducers (led zirconate titanate, PZT) to excite and sense the Lamb waves in composite laminate, which are highly sensitive to transverse cracks. The PZT transducers are arranged as a network of cells, and damage is estimated inside each cell separately. The Gabor wavelet-based continuous wavelet transformation (CWT) is used to process the complicated damage-scattered signals. The concept of centroid is used to locate the damage in two stages: the first stage locates the damaged subcell, and then the damage is accurately located in two-stage detection inside the damaged subcell. Based on accurately estimated location, the damage size is calculated using cubic spline curve (CSC) and elliptical parametric (EP) methods. These methods utilize the same arrangement of transducers, and the same data processing technique at all detection stages. The results indicate that EP method could quantify the damage size with more accuracy than the CSC method..