The aim of this study was to investigate how the personal ecological footprint calculator can more effectively encourage more sustainable behavior. The ecological footprint calculator is used to determine the impact of a person or organization on the environment. Through awareness of the size of that footprint a person may then choose more sustainable behavior. However, it appears that this knowledge hardly ever results in more sustainable behavior. In this study a comparison was done between the effect of the basic version calculator with a modified version. Based on the literature and existing footprint calculators, a modification has been devised that can bring about behavioral change based on the behavioral change principle: social comparison. The participants in the study (89 students and alumni from the Open University) completed the footprint calculator three times over the course of six months to measure the changing ecological footprint. Participants received either the basic version or the modified version. After the third measurement, an additional questionnaire was also completed in order to be able to explain the measured change in the ecological footprints. Statistical analyses determined whether the footprint changed after the first measurement and whether there was a difference between the group using the basic version and the group using the modified version of the calculator. Only the transport component of the footprint was found to decrease very significantly. A decrease of 0.2 ha between the baseline measurement and the measurement after six months. There appeared to be no significant differences between the basic version or modified calculator groups. In the answers to the additional questions, the participants did report the following learning effects: knowledge change, change of consciousness, change of attitude and change of intention. Participants also reported actions they had taken to reduce their footprint. However, no correlation was found between the actions taken and the measured change in the ecological footprint. Also, high scores on characteristics that are related to behavioral change according to psychological theory did not correlate with a decrease in the ecological footprint. The participants objections and personal preferences, which were frequently mentioned, do seem to offer a plausible explanation for the lack of voluntary behavioral change. The measured decrease in the transport component of the ecological footprint is most likely due to the travel restriction that came into effect halfway through the study to safeguard against the corona pandemic. As a result, the average ecological footprint decreased by about 5% compared to the first measurement. Although some participants said they would start traveling again as soon as it is allowed and safe, more than 20% want to continue to work from the home for one or more days. In that case, the effect could be partly structural. However, behavioral change as a result of calculating one's own ecological footprint with a calculator appears to be too high an expectation.