Why Are There So Many Bulb Types?
Different bulb types exist because headlight designs vary between manufacturers. Each type has a specific base, filament position, and wattage that matches a particular headlight reflector design. Using the wrong type means the bulb physically won’t fit, or if forced in, will produce a dangerous beam pattern.
Headlight Bulbs
| Type | Base | Wattage | Common Use |
|---|---|---|---|
| H1 | P14.5s | 55W | Main beam, fog lights |
| H4 | P43t | 60/55W | Combined dipped/main beam (older cars) |
| H7 | PX26d | 55W | Dipped beam (most common since ~2000) |
| H11 | PGJ19-2 | 55W | Fog lights, some dipped beams |
| H15 | PGJ23t-1 | 55/15W | DRL + main beam (VW Group, Ford) |
| HB3 (9005) | P20d | 60W | Main beam (Japanese/Korean cars) |
| HB4 (9006) | P22d | 51W | Fog lights |
Signalling & Auxiliary Bulbs
| Type | Wattage | Use |
|---|---|---|
| W5W (501) | 5W | Sidelights, number plate |
| P21W (382) | 21W | Brake light, reverse light, indicator |
| PY21W (581) | 21W | Indicator (amber coated) |
| W21W (582) | 21W | Indicator, reverse (wedge base) |
| P21/5W (380) | 21/5W | Combined tail/brake light |
| C5W (239) | 5W | Interior, number plate (festoon) |
How to Find Your Bulb Type
The easiest way is to use our car bulb finder — select your make and model for a complete list of every bulb in your car. Alternatively, check your vehicle handbook or look at the markings on the existing bulb.
Frequently Asked Questions
What’s the most common headlight bulb?
H7 is the most common dipped beam bulb on modern cars. H4 is still used on some budget models.
Can I use H7 instead of H4?
No — they have completely different bases and are not interchangeable. H4 has two filaments (dipped + main beam), while H7 has one.
What do the bulb numbers mean?
The ‘H’ stands for halogen. The number indicates the specific base type and filament design. They don’t indicate brightness or quality.
Are all H7 bulbs the same quality?
No — premium H7 bulbs from Philips or OSRAM produce significantly more light than budget alternatives, while still meeting legal wattage limits.
