Although physicians agree broadly that there is no obligation to provide futile care, there is no consensus, of which I am aware, regarding a definition of futility. Two quantitative approaches to determining futility are proposed, neither of which involves financial costs. First, based on the number of consecutive failures of an intervention, it is possible to calculate the probability of success for the next attempted treatment. The second method uses quality-adjusted life years to balance the burden and benefit of a specific treatment and to determine the probability of success beneath which the treatment is futile. When applied to the use of in-hospital cardiopulmonary resuscitation in patients with metastatic cancer, both of these methods confirm the futility of this intervention.