Headlight Bulb Size Codes Explained: H11, 9005 and H7
Headlight bulb size codes explained: what H11, 9005 and H7 identify, why one bulb has two names, and where your car's own code is printed.
Short answer: here are headlight bulb size codes explained in one paragraph. A code such as H11, 9005 or H7 names a standardized bulb design: its base, its plug and locking tabs, where the light source sits, and its rated wattage. It is not a brightness grade. Two naming systems are in use. The H codes are European (ECE) categories, and the 9000-series numbers are North American, so one bulb can carry two names: OSRAM lists its 9005 bulb under ECE category HB3. On US-market cars, the headlamp lens itself is required to be marked with the bulb type.
The specifications below come from OSRAM's own product data sheets and from the US federal lighting rules, all read on September 25, 2026. They explain how to read a code. Which code your car takes comes from its own documentation or its own headlamp.
What a bulb size code actually specifies
A size code is shorthand for a full specification. When a bulb carries a code, it is built to that code's dimensions, so it fits and sits in the same position in any headlamp designed for it. That position matters as much as the fit: the reflector or projector is shaped around exactly where the light comes from.
The US rules make the logic explicit. Federal regulation 49 CFR 564.2 (read on Cornell Law School's Legal Information Institute, September 25, 2026) says one purpose of the replaceable light source rules is to ensure "that redesigned or newly developed light sources are designated as distinct, different, and noninterchangeable." In other words, a different design gets a different code, on purpose, so it cannot be mistaken for an existing one.
Here is what the code carries for the three bulbs people ask about most, from OSRAM's ORIGINAL LINE halogen data sheets.
| Code | OSRAM order reference | ECE category | Base (cap) | Nominal voltage and wattage |
|---|---|---|---|---|
| H7 | 64210 | H7 | PX26d | 12 V, 55 W |
| H11 | 64211 | H11 | PGJ19-2 | 12 V, 55 W |
| 9005 | 9005 | HB3 | P20d | 12 V, 60 W |
The OSRAM ORIGINAL LINE H11 data page (read September 25, 2026) is a good example of how a maker's sheet lays this out: order reference, ECE category, cap, voltage and wattage, each on its own line.
Notice that H7 and H11 have the same nominal wattage in this table but different bases. They are not interchangeable. The code tells you the fitting, and the fitting is the whole point.
Headlight bulb size codes explained: the two naming systems
Most confusion about bulb codes comes from two systems running side by side.
The H codes (H1, H4, H7, H11 and so on). These are European ECE categories. OSRAM's data pages list "ECE category" as a separate field and put H7 and H11 in it.
The 9000-series numbers (9005, 9006 and others). These are the North American designations. Some of these bulbs also have an ECE category name that starts with HB. OSRAM's page for its 9005 bulb gives the order reference as 9005 and the ECE category as HB3. That is one bulb with two names, not two bulbs.
So when one website says your high beam takes a 9005 and another says HB3, they may well agree. The table above lets you check that kind of pairing against a maker's own sheet rather than a forum.
How to read the parts of a code
A bulb box or listing often carries several codes at once. Only one of them is the size code.
| What you see | What it is | Example |
|---|---|---|
| H7, H11, HB3 | The ECE category, which is the size code | H11 |
| 9005 | The North American designation, also a size code | 9005 (same bulb as HB3) |
| PX26d, PGJ19-2, P20d | The base, also called the cap. It describes the fitting only | PGJ19-2 on an H11 |
| 64210, 64211 | A maker's own order number | OSRAM 64210 is an H7 |
| A letter added after the code | Can mark a separate variant of that code | H11B |
| Words or letters for a product line | Marketing names for the maker's range | "Long life" versions |
Two traps come out of this table.
A maker's order number is not a size code. OSRAM's H7 is order reference 64210. A parts site that lists "64210" and another that lists "H7" are describing the same bulb, but only one of them is naming the size.
Read a suffix as part of the code. Treat H11 and H11B as different bulbs unless your car's documentation says otherwise. The US rule quoted above explains the caution: new designs get distinct, noninterchangeable designations, so a code that looks almost the same is not proof of a match.
Why two websites give your car two different bulb numbers
This is the question most people arrive with. There are four common reasons, and it pays to work through them in order.
- The same bulb, named twice. One site uses 9005 and the other HB3, or one gives a maker's order number and the other the size code. Check the pairing against a maker's data sheet.
- Different beams. Low beam, high beam and fog lamp can each take a different bulb on the same car. A lookup that says "headlight" may be answering for a different beam than the one you need.
- A different headlamp design. If your model was offered with more than one headlamp design, across trims or model years, each design has its own bulb list. Our guide on how to tell what trim your car is helps you pin down which version you have, and model year versus build date explains why a car can sit on either side of a mid-year change.
- A plain error. Some sites copy tables from each other, errors included. Our piece on why car specs differ between websites covers how to tell a real difference from a copied mistake.
The fix for all four is the same: stop comparing websites and read your own car.
Where your car's own bulb code is printed
These sources belong to your car, not to a lookup table. Use them in this order.
On the headlamp lens (US-market cars)
This is the source most people never think to check. The US lighting standard, FMVSS No. 108 at 49 CFR 571.108 (read September 25, 2026), requires in paragraph S6.5.3.4.1 that "the lens of each replaceable bulb headlamp must bear permanent marking in front of each replaceable light source with which it is equipped." The marking states the bulb type. The one exception, in S6.5.3.4.1.1: "No marking need be provided if the only replaceable light source in the headlamp is type HB1."
The marking can be small, so look closely in good light. This rule is a US federal requirement. Cars built for other markets follow their own rules, so do not assume the same marking is there.
On the old bulb
Check the old bulb's base or flange for a printed type. If you are replacing a failed bulb, the old one is direct evidence, provided it is the original type. A previous owner may have fitted something else.
Let the headlamp cool before you reach in, and follow the handling instructions on the new bulb's packaging.
In the owner's manual
Look in the owner's manual's specifications or maintenance section for a bulb chart. If you do not have the manual, our list of where to get your owner's manual free, by manufacturer shows each maker's source.
From the dealer parts department
A dealer can look up the bulbs for your exact car from its VIN, which settles any trim or headlamp-design question.
What the code does not tell you
A size code is a fitting and a design, not a verdict on everything else.
- It is not a brightness rating. Bulbs sold under the same code in different product lines can differ in output and life. The maker's data sheet gives the rated output for that specific product, and OSRAM lists luminous flux as its own field.
- It does not describe LED or HID products the same way. An LED product sold "for H11" shares the H11 base, but it is not the halogen H11 design the code was written around. Whether it is legal and whether it lights the road properly in your headlamp are separate questions from fit.
- It does not tell you which beam. A correct code for the fog lamp is the wrong answer for the low beam.
If the headlamp still does not work with the right bulb fitted, the problem is not the code. That is a fault for a shop to trace.
Frequently asked questions
Are 9005 and HB3 the same bulb?
Yes. OSRAM's data page for its 9005 bulb gives the order reference as 9005 and the ECE category as HB3, with a P20d base at 12 V and 60 W. The two names come from the North American and European systems.
Can I use an H11 bulb in place of an H7?
No. OSRAM's data sheets show the H7 on a PX26d base and the H11 on a PGJ19-2 base. The bases are different, so the bulbs do not fit the same headlamp, even though both are rated at 55 W.
What do letters after the code, like H11B, mean?
A letter added to a code can mark a separate variant. Treat H11 and H11B as different bulbs unless your owner's manual or the dealer says your headlamp takes either.
Where is the bulb size written on my car?
On a US-market car, FMVSS No. 108 requires the headlamp lens to carry a permanent marking of the bulb type in front of each replaceable bulb, except where the only bulb is an HB1. The old bulb's base and the owner's manual bulb chart are the other two places to check.
Why does a parts site list a five-digit number instead of H7?
That is often the maker's own order number. OSRAM's H7 halogen bulb, for example, is order reference 64210. Check the size code printed alongside it before you buy.
