Subaru Forester Back Up Light Bulb Size

The Subaru Forester back up light utilizes 1157, 12961, 921, 7440, and 1156 bulb sizes depending on the specific production version. Available information covers the full range from 1998 to 2024.

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

If US Type and EU Type show the same value, a direct cross-reference for this bulb is not available or the data is insufficient.

Years	US Type	EU Type	Shop
2023-2024	1157	P21/5W	Check Price
2021	12961	12961	Check Price
2014-2020	921	W16W	Check Price
2009-2013	7440	W21W	Check Price
2001-2008	921	W16W	Check Price
1998-2000	1156	P21W	Check Price

Bulb Specifications

Description	Type	Shop
ANSI standard (US & Canada). Dual-filament bulb with BAY15d bayonet base. 12V, 21W/5W.	1157	Check Price
ECE standard (Europe & worldwide). Dual-filament signalling bulb with BAY15d bayonet base. 12V, 21W/5W.	P21/5W	Check Price
Philips part number. Miniature wedge bulb (T10) with W2.1x9.5d base. 12V, 5W.	12961	Check Price
ANSI standard (US & Canada). Wedge bulb (T15). 12V, 16W.	921	Check Price
ANSI standard (US & Canada). Single-filament wedge bulb (T20). 12V, 21W.	7440	Check Price
ANSI standard (US & Canada). Single-filament bulb with BA15s bayonet base. 12V, 21W.	1156	Check Price
ECE standard (Europe & worldwide). Single-filament signalling bulb with BA15s bayonet base. 12V, 21W.	P21W	Check Price

Other Locations

Additional Notes

The 921 bulb is the most frequently specified size across the Subaru Forester backup light fitment data, appearing across 2001-2008 and 2014-2020 model years. It is an ANSI-standard T15 wedge bulb rated at 12V and 16W.
The 7440 is a single-filament T20 wedge bulb rated at 12V and 21W. It shares the same wattage as the 1156 and the higher filament of the 1157, but its T20 wedge base is physically distinct from the bayonet bases used by those two bulb types, making cross-substitution impossible without an adapter.
The 1157 specified for the 2023-2024 Subaru Forester is a dual-filament bulb with a BAY15d bayonet base, rated at 12V with filaments drawing 21W and 5W respectively. Its dual-filament design and BAY15d base make it incompatible with single-filament BA15s sockets.
The 1156, specified for the 1998-2000 Forester, is a single-filament bulb with a BA15s bayonet base rated at 12V and 21W. Although it shares the same wattage as the 1157, the 1156 has only one filament and uses a single-contact base, which is not interchangeable with the dual-contact BAY15d base of the 1157.
The 12961, specified for the 2021 Forester, is a Philips-designated miniature T10 wedge bulb with a W2.1x9.5d base rated at 12V and 5W. At 5W, it draws significantly less power than the 921, 7440, 1156, and 1157 types also found in this fitment data.
The wedge-base bulbs in these specifications, the 921, 7440, and 12961, differ from one another in both physical size and wattage. The T10 (12961), T15 (921), and T20 (7440) designations indicate progressively larger wedge bodies, and sockets are sized to match each specific form factor.
Three distinct base types appear across the Forester backup light specifications: the wedge base (921, 7440, 12961), the BA15s single-contact bayonet base (1156), and the BAY15d dual-contact bayonet base (1157). Each base type requires a socket built to that specific configuration.
The 921 and 7440 are both ANSI-standard wedge bulbs operating at 12V, but the 7440 draws 21W compared to the 921's 16W. Despite both using wedge bases, their differing T15 and T20 body sizes mean they are not directly interchangeable.