This paper aims to assess the value of impact perceptions as an indicator of social carrying capacity in the heritage town of Besalú, Spain. Additionally, it assesses the impact tourism dependence and other socio-demographic variables have on this indicator. Design/methodology/approach A literature review on social exchange theory (SET) and carrying capacity related to impact perceptions is presented. The method was a survey, with a questionnaire based on the literature review and in-depth interviews. The results have been analyzed statistically to determine the links between perceptions and socio-demographic variables. Using statistical tools, perceptions are compared to three indicators that have been used to determine capacity in literature: willingness to accept more tourism, tourism pressure and the tourist function index. Findings The willingness of residents to enter into, and remain, in an exchange relationship is affected primarily by tourism dependence, and to a lesser extent by gender and education. Additionally, impact perceptions do not correspond to a willingness to accept more tourists. The impacts of tourism on conservation show greater consensus, while impacts on the availability of space for residents show links to other capacity indicators. Originality/value This study enhances the body of knowledge on social carrying capacity in heritage towns, by focusing on a regionally prominent day-tripper heritage town facing high tourism pressure which is Besalú. From a theoretical perspective, this study attempts to merge carrying capacity and SET, thus linking sustainability to social exchange. It also highlights the importance of a gender-based perspective in sustainability