Mazda 6 Back Up Light Bulb Size

The Mazda 6 back up light bulb uses 7440 and 921 sizes depending on the vehicle configuration. The replacement chart covers 2003 through 2017 production years with corresponding bulb size specifications.

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
2014-2017	7440
2006-2013	921
2003-2004	921

Bulb Specifications

Description	Bulb Size
ANSI standard (US & Canada). Single-filament wedge bulb (T20). 12V, 21W.	7440
ANSI standard (US & Canada). Wedge bulb (T15). 12V, 16W.	921

Other Locations

Additional Notes

The Mazda 6 backup light specifications cover model years 2003-2017, with two distinct bulb types used across that span.
The 921 bulb is the more widely used of the two types in these specifications, appearing across the 2003-2013 model years, with the exception of 2005.
The 7440 bulb is specified for the 2014-2017 Mazda 6, representing a shift from the 921 used in earlier model years.
Both the 7440 and 921 are ANSI-standard wedge bulbs rated at 12 volts, making them compatible with standard automotive electrical systems in the US and Canada.
The 7440 is a T20 single-filament wedge bulb rated at 21 watts, while the 921 is a T15 wedge bulb rated at 16 watts. The two types differ in both physical size and wattage, making them non-interchangeable.
The T20 and T15 designations refer to the outer width of the wedge base, with T20 being the larger of the two. A T15 bulb will not seat correctly in a T20 socket, and vice versa.
The wattage difference between the 7440 (21W) and the 921 (16W) means the two bulbs draw different amounts of current. Substituting one for the other could affect circuit load and potentially trigger fault warnings on vehicles with bulb-out detection systems.
Because the 7440 and 921 share the same 12-volt operating voltage, voltage alone is not a sufficient basis for determining interchangeability between the two types.