While previous research has examined economic motivations for renting personal possessions, the calculative processes owners use remain understudied. We explored how consumers calculate and repurpose their possessions as assets. Through a qualitative analysis of interviews with seven Airbnb hosts and 37 owners renting various possessions, plus 154 Facebook posts from ‘Airbnb propriétaires France,’ we identified four key calculative operations: extraction, qualification, computation, and protection. Our findings reveal a dual pathway—platforms and closed circles—through which mundane possessions become profitable, despite owners’ suboptimal calculations. By including the protection and selective exclusion of possessions, we extend the sociological theory of calculation and improve our understanding of proximity rentals. Overall, calculation generates three benefits: economically, as owners always consider rental revenues significant; ecologically, as even small compensation motivates owners to circulate private goods; and socially, as mutual exchanges between strangers and acquaintances escape gift economy constraints and debt obligations.