Ford Focus Turn Signal Bulb Size

Additional Notes

• The Ford Focus front turn signal uses the 7440 bulb across the 2012-2018 model years, making it the most consistently specified bulb type in these specifications. The 7440 is a single-filament T20 wedge bulb rated at 12V and 21W under the ANSI standard applicable to the US and Canada.
• The rear turn signal of the Ford Focus uses the 3757NA bulb across the 2012-2018 model years. The 3757NA is a dual-filament T25 wedge bulb with natural amber glass, rated at 12V under the ANSI standard for the US and Canada.
• The dual-filament design of the 3757NA rear turn signal bulb means it carries two separate filaments within a single housing, which allows one bulb to serve more than one lighting function simultaneously.
• The natural amber glass designation on bulbs such as the 3457NA, 3357NA, and 3757NA indicates that the amber color is produced by the glass envelope itself rather than by a coating or lens filter. This is the meaning of the "NA" suffix in those ANSI designations.
• The Ford Focus (2011) front turn signal uses the 3457NA, a dual-filament T25 wedge bulb with natural amber glass rated at 12V and 27W/7W. This differs from the single-filament 7440 used in the 2012-2018 model years, meaning the two bulb types are not interchangeable despite both serving the front turn signal position.
• The 2009 Ford Focus front turn signal uses the 3357NA, which is a single-filament T25 wedge bulb with natural amber glass rated at 12V and 27W. The 2008 and 2010-2011 model years use the 3457NA in the same position, and while both share the T25 form factor and natural amber glass, the 3357NA is single-filament while the 3457NA is dual-filament, making them functionally distinct.
• The rear turn signal of the Ford Focus uses the 3057 for the 2010-2011 model years. The 3057 is a dual-filament T25 wedge bulb rated at 12V and 27W/7W, without the natural amber glass of the 3757NA used in later years.
• The Ford Focus (2008-2009) rear turn signal uses the 3157, a dual-filament T25 wedge bulb rated at 12V and 27W/7W. The 3157 and 3057 share the same wattage ratings and T25 form factor, though they carry different ANSI designations and are not guaranteed to be interchangeable.
• All bulb types listed in these specifications conform to the ANSI standard as applicable to the US and Canada, and all operate at 12 volts, consistent with standard automotive electrical systems.
• The T20 and T25 designations refer to the tubular wedge base size of the bulb. The 7440 uses the smaller T20 base, while all other bulbs in these specifications use the larger T25 base. A T20 bulb cannot be substituted into a socket designed for a T25 bulb, and vice versa.