In this report, we provide a quantitative description for 2 aspects of the mouse piriform cortex. First, we give volumetric estimates of regions within the anterior and posterior piriform cortex. Second, we estimate the neuronal densities in each of these regions. From these two estimates, we calculate that the mouse piriform cortex contains around half a million neurons equally distributed over the anterior and posterior piriform cortex. Quantitative descriptions such as these are important because they make it possible to construct realistic models, and they provide a constraint that theories of the olfactory circuit must fulfil. We show how quantitative descriptions can be useful for modelling by using our data to refine and improve earlier models of piriform cortex activity.