How do I know what size bulb my car has?
The quickest way is to check your owner’s manual or inspect the bulb itself for a size code such as H11, 9005, or H4. If you don’t have the manual handy, look up the exact bulb size by entering your car’s make, model and year (or VIN) into a reputable parts catalog or by contacting the dealership.
Bulb sizing can vary by function (headlights, fog lights, turn signals) and by model year, and some cars use sealed assemblies or require whole-module replacements. The guide below lays out reliable ways to identify the correct size and avoid common mistakes.
Identify the bulb size from official sources
Start with primary references and check for exact part numbers or codes for each lighting function.
- Consult the owner’s manual or the vehicle’s service booklet for the precise bulb type and size for each function (low beam, high beam, fog light, turn signal).
- Inspect the bulb you’re replacing: remove the lamp and read any markings on the base or glass (common codes include H11, 9005, 9006, H4, etc.).
- Use the vehicle’s VIN or exact make/model/year in a trusted parts catalog or the dealership’s lookup tool to confirm OEM sizes for each function.
- Be aware of possible variations: some cars use different sizes on the left and right headlights or have separate requirements for fog lights.
- Verify compatibility before purchase by double‑checking wattage, voltage (12V is standard for most cars), and connector type.
Concluding: Relying on official sources—manuals, OEM part lookups, and stamped bulb codes—provides the most accurate starting point for replacement bulbs.
Reading bulb markings: what the codes mean
Many halogen bulbs carry a size code on the metal base or glass, such as H11, 9005, 9006, H4, or H7. These codes identify the bulb's size and pin configuration, which determine fitment in the housing and the electrical connection. When you find a marking, it’s typically sufficient to search that exact code for your vehicle's function, but always cross‑check with the manual or a retailer’s compatibility tool.
When manuals aren’t available: practical shortcuts
If the manual is missing or you can’t access the bulb, these quick methods help you identify the correct size.
- VIN-based lookup or make/model/year search on reputable auto‑parts sites to pull the correct bulb sizes for each function.
- Ask a parts counterperson or your mechanic to confirm the exact bulb type; bring the car’s details or VIN to speed up the check.
- Note each lighting function separately (headlights, fog lights, turn signals, daytime running lights) since sizes often differ by function.
Concluding: When official documents aren’t available, cross‑checking multiple reputable sources and confirming function‑by‑function helps prevent buying the wrong bulb.
VIN lookup and retailer databases
Entering the VIN into a manufacturer or major retailer’s lookup tool yields model‑specific bulb sizes, including regional variations. Always verify with at least one additional source, especially if you drive a newer model with nuanced lighting configurations or an unusual bulb lineup.
Common sizes you might encounter (with caveats)
Some sizes appear frequently across many models, but there are plenty of exceptions. Use the methods above to verify your exact car.
- H4 (dual filament) – found on older or certain European vehicles; combines high and low beams in one bulb.
- H7 – common for low-beam headlights on many European cars.
- H11 – common for low-beam or some fog lights on a wide range of 2000s–2020s models.
- 9004/9005 (HB3/HB1) and 9006 (HB4) – often used for higher-beam or specific fog configurations.
- H13 – used in some trucks and SUVs with dual filament configurations.
Concluding: sizes vary by region, model year, and function; always confirm with your vehicle’s official specifications before purchasing.
Practical reminders for replacement
Handling bulbs properly helps maximize longevity and performance, and it reduces the risk of oil contamination or damage during installation.
- Always wear gloves or use a clean cloth when handling bulbs; oils from skin can shorten halogen bulb life.
- Avoid touching the glass portion of halogen bulbs; hold them by the base or use a paper towel.
- Test the new bulb in a dry, cool environment and reassemble the housing securely to prevent moisture ingress.
Concluding: Correct sizing paired with careful handling ensures reliable lighting and avoids early failures.
Summary
To know your car’s bulb size, start with the owner’s manual or the bulb’s own markings, then verify with VIN-based or vehicle‑specific online lookups. If the manual isn’t available, cross‑check multiple reputable sources and confirm function-by-function (headlights, fog lights, signals). When in doubt, consult a dealer or a trusted mechanic. With the right size, you’ll replace bulbs safely and restore proper illumination quickly.
How do I find out what size bulb is in my car?
Every headlight is designated with a bulb size. For a bulb installed in your car, you can find the number stamped or printed on the side of the bulb. It's also listed in the service manual and in an auto bulb guide. Only the correct bulb size will fit in the headlamp housing and connect to the factory wiring.
How do I figure out what headlight bulb I need?
Simply plug in your vehicle's make, model, and year and see which bulbs are compatible. This will show you the headlights that are the right size and fit for your housing. Common headlight bulb sizes include H11, 9005, H4, 9006, and H7.
How do I find out what bulbs my car takes?
You can also look in your vehicle handbook in the lighting section of the manual. If you don't have your registration number or vehicle handbook, you can identify the replacement bulb you need by removing the old one. You should be able to see the bulb's application number, which might begin with a D, H or P.
How do I tell what size my light bulb is?
You can tell a light bulb's size by checking the code printed on its base, where a letter indicates its shape and a number indicates its diameter in eighths of an inch. For example, an A21 bulb has an "A" shape and a diameter of 21/821 / 821/8 inches. Alternatively, you can compare it to the bulb in your fixture, or for other bulb types, look at the base for its specific code (like E26 for a medium screw base or GU10 for a twist-and-lock base).
This video explains how to identify light bulb sizes: 53sAMRE SupplyYouTube · Jul 5, 2020
Using the code on the bulb
- Look for the code: The code is usually printed on the metal or plastic base of the bulb.
- Decode the number: For most common household bulbs, the number after the letter is the diameter in eighths of an inch. For example, an A19 bulb is 19/819 / 819/8 inches in diameter, or about 2.3752.3752.375 inches.
- Decode the letters: The letters indicate the shape of the bulb. Some common ones include:
- A: Standard household shape
- T: Tubular or tube shape (like a T8 or T12 fluorescent bulb)
- R: Reflector bulb
- BR: Bulged reflector bulb
Using the base type code
- Screw-in bases: These are often indicated by an "E" followed by a number that is the diameter in millimeters. For example, an E26 is a medium base that is $26$mm in diameter, and an E12 is a candelabra base that is $12$mm in diameter.
- Other base types:
- GU10/GU24: These use a "twist and lock" mechanism. The number indicates the distance between the pins.
- Pin bases: These have two or more pins that go into a socket. The code often includes a "G" followed by the number of pins and then a number for the distance between them, like G5 (pins are 5mm apart).
If you can't find the code
- Take the old bulb to the store: Bring the old bulb with you to a hardware or lighting store so you can compare it to the new ones.
- Check the fixture: Look for a label or sticker on the light fixture itself, which may contain the correct bulb type and size information.
- Use a smartphone: Take a picture of the old bulb or the fixture's label and show it to an associate at the store for help.
