Headlight Bulb Sizes

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We understand that the process of replacing one’s headlight bulbs can be a daunting task. Ideally, different types of vehicles will require a specific type of headlight bulbs. Some vehicles are suited for the low/high beam combo while others work best with the fog, low beam, and high beam type of bulbs.

It is never surprising to find one type of headlight bulb operating great in one type of vehicle but behaving terribly in another. But we are here for you. Any question that you have about headlight bulbs will be answered. We have a team of professionals who have put their expertise into use to make this replacement bulb size guide a success.

So what is the right bulb type for your vehicle? Car owners need to check the correct wattage and the right bulb type when replacing their current headlight bulbs.

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You can easily use our recommended online bulb finder to figure out the right type of bulb for your vehicle’s model, make, and year.

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Bulbs Guide

When we consider which type of headlight bulb to get for better lighting it is really important to understand whether you need a projector or reflector headlight. Normally a projector headlight would accommodate an H11, 9005 or 9012 single beam halogen light bulb. If you are interested to make to headlights brighter, you may want to opt for an LED light bulb options to replace the halogen counterpart. Problem is there are hundreds of different LED light bulbs and some of them will not fit into the headlight housing or do not produce a good beam pattern.

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Comparing halogen vs LED vs. HID

Halogen headlight is still the main type of headlight found in most cars today. But new technologies such as LED and HID are slowly replacing the halogens headlights. Let’s get into them right away.

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Halogen Headlights

Halogen lights contain a mixture of argon and nitrogen together with a tungsten filament contained in a glass tube designed to withstand high temperatures. As soon as the light bulb comes in contact with the electrical current from the car, the tungsten will be heated generating light in the process.

The automotive world comes as the most common type of headlight bulbs with it being installed in over 80% of the cars. They are mainly preferred for their cheaper prices and the fact that they have a good lifecycle.

But they also come with their own weaknesses being notoriously dim and infective when compared to other lighting options. While a standard halogen bulb will end up producing up to 1300 Lumen, there are still far much better offers on the market.

The very fact they are also highly sensitive to other substances makes them infective. Even touching it with your palm will alter the spread of heat and significantly decrease the lifespan.

High-Intensity Discharge (HID)

Introduced back in the 90s, they are still being used up to date. The HID lamps contain a mixture of rare metals and gases that harmoniously combine to produce blue or white glows. In fact, legislators have made it a requirement that all new cars must have such type of illumination.

The HIDs have many advantages such as a blue light that contributes to the aesthetic beauty. Compared to halogen bulbs, Xenon lamps are much brighter.

Using HID lamps come with an increased vision which improves the reaction time to unforeseen danger ahead, especially at night. From the start they require much power to illuminate but once they are lit, they end up using 25% less power than halogens. Additionally, the fact that they use rare metal means that they are not cheap which makes them be expensive for replacement. Though, in the long run HID lamps still might be cost effective as they last 2-3 times longer than halogen counterparts.


For a majority of car models, the HID lighting system is only used for low beams. This means that the high beam lighting is provided by the halogens light. This is mainly the reason as high beams tend to be switched on and off all the time and HIDs are not adapted to it.

But for vehicles that have bi-xenon headlights, HIDs will be sued to provide both the high and low beam by using a shutter that generally moves up and down when triggered. With the bulb being in position, you will avoid the delay when turning it on.

Moreover, bi-xenon lamps often use two bulbs. This fact alone makes them expensive. The shutter used to move the bulb is vulnerable to wear and tear and can cause malfunction at any given time. The standard Xenon headlights got past this limitation by getting rid of the shutters altogether.

Light emitting diodes (LED)

You may be surprised to learn that LED car lights have been with around since 2004 but only gained popularity in recent years. The main reason why the LED bulbs are so popular is the fact they are very energy efficient. Compared to halogen bulbs that use up to 65W and HIDs using 42W, LED bulbs only require between 15 to 18 watts.

What is even more appealing, the LED bulbs have a longer lifespan (up to 40000 hours) which means they can even outlive your car. Pretty incredible right? LED bulbs are also small in size fitting into the smallest sockets. Their brightness levels are also good falling somewhere in between the Halogen and HID light bulbs. But just like most things, LED bulbs have their own weaknesses. LED bulbs end up creating a small heat at the emitter when they come into contact with the electrical current.

See More: LED vs HID vs Halogen

It can lead to damaging certain parts of the car such as the connectivity and assembly cables. This is the reason why LED headlights require the use of a cooling system together with hit sinks to prevent them from melting. Even more interesting is the fact the cooling system is not positioned on the headlights, but on the engine body instead. This means manufacturers tend to have a hard time installing headlights for certain models making them more expensive when compared to all the other types of lighting system.

Laser headlight

Whenever one mentions the word laser, many minds tend to drift to the world of Star Wars and other science fiction productions. In such cases, lasers are used as a deadly weapon. But when used in a real life, lasers are not that dangerous.

In fact, many automotive experts believe that lasers would be the next big thing to happen to headlight technologies. Lasers are known to be energy efficient as well as producing brighter lights.

But the only problem is lasers are so new on the headlight market and a small number of cars use them. Only rich people who can afford to buy high-end cars can enjoy the power of the laser headlights.

Projector and reflector headlights

Projector headlights are used when one needs more control over the lights beams. Make no mistake, projector headlights and HID headlights are not the same. HID’s do indeed come in one type of projector housing. But not all projector headlight housings will use the HID bulbs.

Reflector headlamp allows the light to come from a bulb positioned at the center of the headlight using shielding the lights off the sides of the housing. Using this type of headlights will allow the light to be spread out in front of the car on the road.

How to Read Bulbs SIgnature

Most often you can find light bulbs with a different designation. It is carried out according to the common European standard ECE. It uses the following encryption:

  • T – miniature base lamp, for example, T4W;
  • R  – light bulb having a base diameter of 15 mm, bulb diameter is 19 mm (R10W);
  • P  – light bulb having a base diameter of 15 mm, and the bulb diameter does not exceed 26.5 mm (P15W);
  • W  – lamp with glass base (W4W);
  • H  – halogen light (H5W);
  • Y – the presence of this letter in front of the number indicates the orange color of the bulb (PY21W).

The procedures for replacing a headlight bulb

  • Start by opening your car’s hood.
  • Slowly turn the power connector at the back of the headlight so as to safely remove it.
  • Slowly twist the dust cover located at the back headlight so as to remove it.
  • Press down the clip that may be holding the bulb in position.
  • Firmly hold the housing of the bulb and remove it.
  • Gently wipe your new bulb with moistened alcohol so as to remove all traces of dust.
  • Insert the bulb housing into position.
  • Now push the bulb into position and ensure that it’s firmly locked into position.
  • Proceed to replace the power connector, dust cover, and the clip if you have them with you.
  • Now turn own your headlights to ensure that they are working effectively.
  • Hurray! You did it!

To make things even worse, some of them are not even as bright as the original halogen bulb. A projector does both beams, low and high, even though it uses a single filament light bulb. Inside a projector there is a shutter that opens and closes to show you all of the light output or only half. So even if you have a basic single filament light bulb you can still get the dual beam out of a projector headlight. This is not the case with the reflector analog. Projectors can make one or two beams depending on the design while reflectors are always one beam. If you want reflector to do both hight and low beam you have to use a different type of a light bulb. Nowadays, a lot of cars can come with a projector and reflector type of headlights on the same vehicle.

For example, you can replace reflector headlights with a projector kit of the same shape. It is a pretty common upgrade because some people like the way the projector looks. Theoretically, it also provides a better beam pattern. Reflectors are pretty simple – a bulb illuminates the chrome area inside, light source bounces off the shiny surface that creates a beam pattern. Generally, it is fairly inefficient and not very focused. At least, not as focused as compared to the projector. The interesting thing about the projector headlights is that they sometimes incorporate the benefits of both technologies. Opposite to a very large horizontal layout found in the reflector, the projector has a very small bowl with the light bulb sitting backward.

The light from the bulb is captured inside this small bowl and gets focused through the lens. The same principle is leveraged when using the magnifying glass in the sun to start a fire except for the fact the desired effect with the lens is to create a razor-sharp beam pattern. There is one big characteristic of the different types of projector lenses dividing them into a single beam and dual beam with the latter one having a solenoid and some wiring coming out. If you give this connector 12 volts the solenoid will be activated inside the projector to lower the cut-off shield. In low beam position, not energized, the shield is upright and creates a sharp cut-off horizontal line.

When switching from low to high beam the solenoid is energized and the shield pulls down opening up the projector lens for 100 percent. In the dual beam projector, this creates high and low beams. In a single beam projector, there is simply one static projector for low beam and either another projector or a reflector for high beam. Some cars might use all three styles. Let us sum up the differences between the reflector and projector headlights. Normally, reflector headlights will use halogen bulbs but there are certain circumstances with a vehicle coming off the factory with a reflector with HID. Same goes for projectors.

It is a 50-50 situation. A lot of factory projector headlights come with a halogen light bulb but a lot of times they have LED or HID. Sometimes you can convert a reflector headlight to LED or HID with just different light bulbs. And sometimes you can do the same thing with the projector. Generally speaking, you are guaranteed an increase in light output if you convert your projector halogen bulb to HID. If you stick with LED the odds are not that good as more and more products are coming to the market which are suitable applications for an LED bulb in a projector. But if you already have projector headlights and you want to make them brighter your best bet is an HID conversion kit.

It is strongly recommended to always wear safety glasses when replacing their headlight bulbs for safety reasons.

We cannot claim to provide a comprehensive headlight bulb guide without mentioning this topic. To start with, always know that the color of the light is always measured in K which is obtained by using the Kelvin scale.

A typical halogen bulb like those found in most cars will be classified as being of warm colors. For it to have an even more temperature, it has to pass through the tinted glass. Now you know why cars that have blue headlight bulbs end up producing white light. But the darker the tint is, the bluer the color will become.

Headlights alignment

How to correctly aim and adjust headlights? Contrary to what many people may be aware of, your car’s headlights are designed in a way that they would end up being a fit in countries that either drive on the left side or the right side.

This is why the headlights used for left-sided traffic always have low-beam headlights that refract to the left. This allows the light to be disbursed in a way that it moves downward as a way of letting the driver see the road without having to blind oncoming traffic. The vice-versa is true for cars that are driven on the right side of the road.


SAE is a type of stamp that is majorly used in the US while the ECE is common for the European nations. The only difference between the two is the allowed light intensity and the permissible amount of glare. For instance, America allows more glare.

Load adjustment

The term load adjustment, whenever used, implies that the headlights will typically adjust themselves bending downwards to avoid dazzling the cars moving in the opposite line.

Understanding wattage

Many people tend to get this aspect absolutely wrong. If you want more light, simply go for more watts. It is that simple. You cannot, for instance, compare the light output of a 40Wlight bulb with a 150 W light bulb.

A marking such as 65/55W means that the low beam is 55W and the high beam is 65W.

Final Remarks

Read More on Car Light Bulbs on Autotk.

Considering the above said, we advise to seek a balance between performance, longevity, and price. Headlight manufacturers tend to charge more for bulbs that are whiter and very bright as well. This means that brighter bulbs with higher color temperature and higher light output cost more. Halogen headlight bulbs end up being white and brighter but do not last long. If you want to try high-end products like HIDs and LEDs headlights bulbs, you will get a great white (brighter) lamps with a solid life span. While a high output halogen bulb is expected to last for a year, LED and HIDs will last between 3 and 4 years. Hopefully, you have all the information you need on headlight light bulbs to make the right decisions.