Devices and methods for measuring size of airways to lung are disclosed. A light-based endoluminal sizing device can comprise a centering tool, a light source, and a marker. A size of an airway can be approximated or determined based on a distance between the marker and the light source when light from the light source intersects the marker at an interface between the marker and the airway wall. In some cases, the size of the airway can be approximated from observing an intersection between a light pattern and the airway wall.
