BMW 650i Back Up Light Bulb Size

The BMW 650i back up light utilizes 921 and P21W bulb sizes for the lighting components located at the rear of the vehicle. Available data for the specified automotive bulbs covers the range from 2006 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
2012-2018	921
2008-2010	921
2006-2007	P21W

Bulb Specifications

Description	Bulb Size
ANSI standard (US & Canada). Wedge bulb (T15). 12V, 16W.	921
ECE standard (Europe & worldwide). Single-filament signalling bulb with BA15s bayonet base. 12V, 21W.	P21W

Other Locations

Additional Notes

The BMW 650i uses two distinct back up light bulb types across its model years: the 921 and the P21W.
The 921 is an ANSI-standard bulb used in the United States and Canada. It follows the T15 wedge form factor and operates at 12V with a 16W output.
The P21W is an ECE-standard bulb common in European and worldwide markets. It uses a BA15s bayonet base, features a single filament, and operates at 12V with a 21W output.
The BMW 650i (2008-2018) uses the 921 bulb for the back up light position, covering the majority of the model's production span.
The 2006-2007 model years use the P21W instead, which draws 21W compared to the 16W rating of the 921, making the two bulbs electrically incompatible as direct substitutes.
The 921 wedge base and the P21W bayonet base are physically non-interchangeable, meaning a bulb from one standard cannot be installed in a socket designed for the other.
The shift from the P21W to the 921 between the 2007 and 2008 model years reflects a change in the bulb standard used for this position on the 650i.
When sourcing a replacement, confirming the exact model year of the 650i is necessary, as the socket type differs between the pre-2008 and post-2007 configurations.