Smart Fortwo Dome Light Bulb Size

The Smart Fortwo dome light utilizes bulb sizes 12961 and 6411 according to the provided technical specifications for the interior lighting components. The available data covers the range from 2008 through 2018 for the specified vehicle.

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
2016-2018	12961
2008-2015	6411

Bulb Specifications

Description	Bulb Size
Philips part number. Miniature wedge bulb (T10) with W2.1x9.5d base. 12V, 5W.	12961
ANSI standard (US & Canada). Festoon bulb, 36mm length, SV8.5 base. 12V, 5W.	6411

Other Locations

Additional Notes

The Smart Fortwo uses two distinct dome light bulb types across its model years: the 6411 festoon bulb for 2008-2015 and the 12961 wedge bulb for 2016-2018.
The 6411 is an ANSI-standardized bulb recognized across the United States and Canada, while the 12961 is a Philips part number designation, reflecting a manufacturer-specific cataloging system rather than a universal standard.
Both bulb types operate at 12 volts and 5 watts, meaning they share identical electrical requirements despite their physical differences.
The 6411 is a festoon-style bulb, which is a cylindrical lamp that seats between two spring-clip contacts at each end rather than inserting into a socket.
The 6411 has a 36mm length and an SV8.5 base, where SV8.5 refers to the contact cap width of 8.5mm used on festoon bulbs.
The 12961 is a T10 miniature wedge bulb, a form factor in which the glass envelope itself is pinched at the base to form a wedge shape that friction-fits into a socket.
The 12961 uses a W2.1x9.5d base, a designation indicating a wedge base with a 2.1mm wire contact width and a 9.5mm insertion depth.
The 6411 and 12961 are not interchangeable. The festoon and wedge base types require physically different socket designs, and substituting one for the other is not possible without modifying the fixture.