Identifying students' difficulties in understanding Gauss's and Ampere's laws is important for developing educational strategies that promote an expertlike understanding of the field concept and Maxwell's equations of electromagnetic phenomena. This study aims to analyze and compare students' understanding of symmetry when applying Gauss's and Ampere's laws to calculate the electric or magnetic field. We conducted a study to analyze how students reason regarding the symmetry conditions necessary to apply Gauss's or Ampere's laws to calculate the electric or magnetic field in three inverse problems. We applied two open-ended questionnaires with parallel surface features, one for Gauss's law and the other for Ampere's law, to 322 engineering students. The three inverse problems present different scenarios with the common characteristic that there is no sufficient symmetry to solve the electric or magnetic field from its corresponding equation. We analyzed students' answers with a phenomenographic approach, focusing on students' answers to a yes or no question and their reasoning. The main findings of the study are the descriptive categories of understanding and the comparison of the categories between contexts (outcome space). The correct reasoning is identifying the necessary symmetry to apply Gauss's or Ampere's law. The other categories refer to the surface features of each scenario to explain students' answers, applying Gauss's or Ampere's law in an oversimplified way and thinking that it would be possible but more complicated in these scenarios. The descriptive categories are related to some of the difficulties previously reported in the literature with standard problems involving Gauss's and Ampere's laws. However, inverse problems elicited variations in the types of reasoning. The comparative analysis between the electricity and magnetism contexts indicates that analyzing currents can be more challenging for students than point charge analysis.