Subject-specific computational and experimental models of hemodynamics in cerebral aneurysms require the specification of physiologic flow conditions. Because patient-specific flow data are not always available, researchers have used 'typical' or population average flow rates and waveforms. However, in order to be able to compare the magnitude of hemodynamic variables between different aneurysms or groups of aneurysms (e.g. ruptured versus unruptured) it is necessary to scale the flow rates to the area of the inflow artery. In this work, a relationship between flow rates and vessel areas is derived from phase-contrast magnetic resonance measurements in the internal carotid arteries and vertebral arteries of normal subjects.