Several inlet configurations are utilized on culvert barrels. These include both prefabricated and constructed-in-place installations. Commonly used inlet configurations include the following:

When selecting various inlet configurations, structural stability, aesthetics, erosion control, and fill retention should be considered.

Culvert hydraulic capacity may be improved by selecting appropriate inlets. Because the natural channel is usually wider than the culvert barrel, the culvert inlet edge represents a flow contraction and may be the primary flow control. A more gradual flow transition lessens the energy loss and thus creates a more hydraulically efficient inlet condition. are more efficient than square edges. and , commonly referred to as improved inlets, further reduce head loss due to flow contraction. Depressed inlets, such as slope-tapered inlets, increase the effective head on the flow control section, thereby further increasing the culvert efficiency.