<p>A visual operational guidance, known as a polar chart, shows considerable potential for preventing excessive roll motion caused by parametric roll. This study utilizes a method based on the extended Grim’s effective wave (EGEW) theory for preparing a polar chart and validates it using experimental data. Although it can also be prepared by nonlinear seakeeping simulation in irregular waves, the proposed approach is computationally more efficient. The study compared experimental data and estimated parametric roll under both longitudinal and quartering wave conditions, the latter being particularly critical for large container ships. Additionally, a 6-degree-of-freedom (6-DOF) motion simulation based on three-dimensional potential theory was employed for comparison. The results demonstrated that the polar chart yield more conservative estimates than both the experimental data and the 6-DOF simulation, effectively covering the range where parametric roll is likely to occur. The findings could contribute to the development of safer operation, thereby reducing the risk of parametric roll.</p>