Ram 4500 License Plate Bulb Size

The Ram 4500 license plate light uses 194 and 1157 bulb sizes for the rear exterior lighting components. Data for the specified vehicle covers the period from 2011 through 2018.

The year-by-year compatibility chart below provides a quick reference to verify the correct bulb size for your vehicle.

Bulb Size by Year Range

Years	Bulb Size
2018	194
2011-2012	1157

Bulb Specifications

Description	Bulb Size
ANSI standard (US & Canada). Miniature wedge bulb (T10). 12V, 3.78W.	194
ANSI standard (US & Canada). Dual-filament bulb with BAY15d bayonet base. 12V, 21W/5W.	1157

Other Locations

Additional Notes

The Ram 4500 license plate position uses two distinct bulb types across its model years: the 194 and the 1157, both of which conform to ANSI standards recognized in the United States and Canada.
The 194 is a T10 miniature wedge bulb rated at 12 volts and 3.78 watts. Its wedge base design means it is retained by spring tension within the socket rather than by a twist-lock or bayonet mechanism.
The 1157 is a dual-filament bulb fitted with a BAY15d bayonet base, rated at 12 volts with a 21W/5W filament configuration. The dual-filament construction serves two independent brightness levels from a single bulb.
The BAY15d base of the 1157 features two offset pins, which physically prevent incorrect insertion into the socket. This offset design is a deliberate fitment control that distinguishes it from single-filament bayonet types.
The Ram 4500 (2018) uses the 194 bulb for the license plate position, while the 2011-2012 model years use the 1157. These two bulb types are not interchangeable due to differences in base design, wattage, and filament count.
The wattage difference between the two bulbs is substantial. The 1157 draws up to 21 watts on its primary filament, compared to 3.78 watts for the 194, reflecting a significant difference in socket and circuit design between the affected model years.