Audi Q3 Brake Bulb Size

The Audi Q3 brake component utilizes a P21W bulb size for the lighting system across various production periods. Available data for the specified vehicle covers the span from 2017 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

Years	US Type	EU Type	Shop
2023-2024	1156	P21W	Check Price
2020-2021	1156	P21W	Check Price
2017-2018	1156	P21W	Check Price

Bulb Specifications

Description	Type	Shop
ECE standard (Europe & worldwide). Single-filament signalling bulb with BA15s bayonet base. 12V, 21W.	P21W	Check Price
ANSI standard (US & Canada). Single-filament bulb with BA15s bayonet base. 12V, 21W.	1156	Check Price

Other Locations

Additional Notes

The P21W is the brake bulb size specified for the Audi Q3 across all listed model years.
P21W is an ECE-standardized bulb type, meaning it conforms to the Economic Commission for Europe regulations that govern lighting equipment used in vehicles sold across European and worldwide markets.
The bulb operates on a 12-volt electrical system and draws 21 watts, which is a standard power rating for single-filament signalling applications such as brake lights.
P21W uses a BA15s bayonet base, a single-contact fitting where the "s" denotes a single pin offset, distinguishing it from double-contact variants like the BA15d.
Because the BA15s base is a single-contact design, it is not interchangeable with physically similar bases that carry two contacts, even when the outer housing appears to fit the socket.
The single-filament construction of the P21W means the bulb serves one lighting function only, as opposed to dual-filament types such as the P21/5W, which handle two functions from a single unit.
The 2021-2024 and 2017-2018 model year groups each share the same P21W specification, indicating consistent brake bulb fitment within those respective ranges.