BMW M240i Back Up Light Bulb Size

The BMW M240i back up light utilizes 7440 and P21W bulb sizes for the specified lighting components. Data for the provided specifications covers the range from 2017 through 2020.

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
2019-2020	7440
2017-2018	P21W

Bulb Specifications

Description	Bulb Size
ANSI standard (US & Canada). Single-filament wedge bulb (T20). 12V, 21W.	7440
ECE standard (Europe & worldwide). Single-filament signalling bulb with BA15s bayonet base. 12V, 21W.	P21W

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Additional Notes

The BMW M240i uses two distinct bulb types for the back up light across its model years: the 7440 and the P21W.
Both the 7440 and P21W operate at 12 volts and consume 21 watts, making them electrically equivalent despite their physical differences.
The 7440 follows the ANSI standard used in the United States and Canada. It is a single-filament wedge bulb built to the T20 form factor.
The P21W follows the ECE standard used in Europe and worldwide. It is a single-filament signalling bulb fitted with a BA15s bayonet base.
The 2019-2020 BMW M240i specifies the 7440 bulb for the back up light position.
The 2017-2018 M240i specifies the P21W bulb for the same position.
The wedge base of the 7440 and the BA15s bayonet base of the P21W are physically incompatible with each other, meaning the two bulb types are not interchangeable despite sharing the same voltage and wattage ratings.
The BA15s designation on the P21W indicates a single-contact bayonet cap with a 15mm base width, a base type common in European automotive lighting applications.