Although response effort is considered a dimension of the cost to obtain reinforcement, little research has examined the economic impact of effort on demand for food. The goal of the present study was to explore the relationship between effort and demand. Three Sprague Dawley rats were trained to press a force transducer under a series of fixed-ratio schedules (1, 10, 18, 32, 56, 100, 180, 320, and 560) under different force requirements (5.6 g and 56 g). Thus, nominal unit price (responses / food) remained constant while minimal response force requirements varied. Using a force transducer allowed the measurement of responses failing to meet the minimal force requirement (i.e. “subcriterion responses”), an advantage over prior approaches using weighted levers to manipulate effort. Consistent with prior research, increasing the unit price decreased food consumption, and raising minimum force requirements further reduced demand for food. Additionally, increasing the force requirement produced subcriterion responses. Analysis indicated that subcriterion responses did not create incidental changes in unit price. Obtained force data revealed that including obtained forces in unit price calculations provided better predictions of consumption when compared to using criterion force requirements.