Fibrosis can cause structural remodeling of cardiac tissue and increase the susceptibility to atrial fibrillation (AF). The objective of this study is to determine the density and location of fibrosis by analyzing the P-wave morphology derived from 50 simulations of an atrial model with varying fibrosis characteristics. The density of fibrosis can be determined using sample entropy (SE), with a tendency for entropy to increase with higher fibrosis density. The SE value was 1.16 times higher for cases with 5-7% fibrosis density compared to those with 0-1%. Additionally, the area under the curve can be used to identify the location on the atria affected by fibrosis. This study provides essential insights into the relationship between P-wave morphology and fibrosis, paving the way for personalized treatment approaches based on fibrosis density and location.