Understanding Metric License Plate Screw Sizes: A Comprehensive Guide

Choosing the right size license plate screw is crucial for proper installation and security. The standard size is a 1/4-14-3/4 inch self-tapping screw, which is commonly used for North American license plates and fits most vehicles. However, there are also metric sizes, which are used in many countries outside of North America, including Europe and Asia. These metric screws are measured in millimetres and are commonly available in sizes M6 and M8. M6 screws are suitable for most standard vehicles, while M8 screws are larger and more robust, often used for heavy-duty applications.

It's important to note that different car brands may require different screw types and sizes, and some vehicles may have specific requirements for the number of license plates, their location, and the type of screws that can be used.

Metric vs standard sizes

When it comes to metric vs. standard screw sizes, there are a few key differences to note. Firstly, “standard” typically refers to US fasteners, which use the imperial measurement system with units in inches. In contrast, metric screws use the decimal-based system and are measured in millimetres (mm).

The major difference between metric and standard screws lies in how their threads are specified. Standard fasteners are classified as either Unified National Coarse Thread (UNC) or Unified National Fine Thread (UNT), whereas metric threads are not specified this way but are comparable to UNC threads.

Another distinction is in their measurement systems. Metric screws are measured in metric units, with pitch specified in millimetres (mm)—the distance between the peaks of two adjacent threads. Standard screws, on the other hand, are measured in imperial units by TPI (threads per inch).

Metric screw sizes are commonly used in many countries, including Europe and Asia. They are designated with an "M" followed by a number, such as M6 or M8, which are often used for license plates. M6 screws have a diameter of 6mm and are suitable for most standard vehicles, while M8 screws, with an 8mm diameter, are used for larger license plates or when extra strength is required.

In the US, standard screw sizes are prevalent for license plates. These are designated with a number followed by a hashtag, such as #14, which has a diameter of approximately 0.242 inches or 6.15mm.

It's worth noting that some license plate frames may have pre-drilled holes designed for specific screw sizes, so it's important to ensure compatibility.

When choosing license plate screws, it's crucial to consider vehicle manufacturer recommendations, material, strength, and anti-theft features. Stainless steel is a popular choice for its durability and corrosion resistance, while anti-theft screws require specialised tools for installation and removal, deterring theft.

In summary, understanding the differences between metric and standard screw sizes is essential for selecting the appropriate screws for your license plate, ensuring a secure and proper installation.

Screw materials

The choice of screw material is critical for the success of any project, whether you are a DIY enthusiast or a professional. Here is a detailed guide on screw materials to help you compare metric license plate screw sizes:

Steel

Steel is the most common material for manufacturing screws due to its low cost compared to other options. It is suitable for indoor projects but not recommended for outdoor use, especially in exposed conditions.

Copper

Copper screws offer excellent resistance to corrosion. They are ideal when the screw will be exposed to the elements, ensuring long-term durability.

Aluminum

Aluminum is known for its lightweight properties, making it the lightest fastener option available. However, it is not as durable as other materials.

Titanium

Titanium screws provide a blend of strength and lightness, making them ideal when you need a robust yet lightweight fastener. They come at a premium price but offer excellent performance.

Stainless Steel

Stainless steel screws are a popular choice for license plates due to their durability and corrosion resistance. They are suitable for both indoor and outdoor use and are commonly used in heavy-duty applications.

Zinc-Plated Steel

Zinc-plated steel screws offer good corrosion resistance and are often more affordable than stainless steel options. They are suitable for both indoor and outdoor use.

Nylon

Nylon screws are lightweight and non-corrosive. They are commonly used in electrical applications but may not provide the same strength as metal screws.

When choosing screw materials, it is important to consider the intended use, environment, and load-bearing requirements. Additionally, coatings can be applied to screws to enhance their properties, such as corrosion resistance or aesthetic appeal.

Screw head types

The head of a screw is an important feature as it significantly impacts the form, fit, and function of the fastened joint. Screw head types can be divided into two basic designs: countersunk and non-countersunk.

Countersunk

Countersunk screws have heads that are angular underneath and require countersinking to prevent splitting wood. Countersunk screw heads sit flush against a surface with little to no protruding parts. The three main types of countersunk screws are:

• Flat: These sit entirely flush with the material’s surface, preventing things from catching on them. Flat head screws are used in wood-worked consumer products such as cabinetry and woodworking applications.
• Oval: Sometimes called raised screw heads, oval heads have a similar angle to flat heads and therefore require countersinking. This decorative dome-shaped head is often used for switch coverings.
• Bugle: Bugle heads are used primarily on drywall, wood decking, and plasterboard screws. This shape reduces damage by distributing stress over a wider surface than flat heads.

Non-Countersunk

Non-countersunk screws are flat under the head and do not need countersinking. They have fully exposed heads that sit on the surface. There are many more varieties of non-countersunk screws, including:

• Hex: Hex heads are designed to allow for greater torque and typically require a wrench or socket for installation.
• Modified Truss: Also known as wafer head screws, K-Lathe screws, or round washer head screws, they combine the benefits of the pan head design with an attached washer built onto the head to increase the head diameter.
• Button: Button screws are a rounded design used in socket-driven screws and have recently grown in popularity with Torx drive recesses.
• Domed: The flat inner part helps this dome-shaped head sit flush on the surface. Dome heads are a popular screw head type used to enhance various projects with an appealing aesthetic.
• Pan: Pan heads are the most common type of rounded screws and are used in many applications that require a flat-bottomed screw.
• Round: Although this design is becoming less common, round screw heads offer a rounded appearance.
• Fillister: Fillister heads have a slightly rounded top and tall cylindrical sides, giving them a deeper drive slot than round or pan head screws.
• Truss: Truss head screws have a wider and slightly rounded surface. They generally provide a lower profile and larger bearing surface than round or pan heads and are typically used for sheet metal.
• Flange: This style features a circular flange directly underneath the head, which can take the place of a washer.
• Pancake: Pancake head screws are distinguished by their round, low-profile heads, which make them ideal for fastening panel clips to wood, Panel Clip screws, and other applications such as building carports or barns, and roofing.
• Socket Cap: These heads are unique to socket drive recesses and install flush against the surface, providing a smooth appearance.
• Square: Square heads are used in bolts and screws and typically require a wrench for installation and removal.

Some head styles combine features to create new shapes, such as slotted hex, hex washer, slotted hex washer, and round washer.

Screw sizes for different car brands

License plate screw sizes vary depending on the car brand and model. While the standard license plate screw size for most vehicles is 1/4-14-3/4 inch, certain car brands require different screw sizes and types. Here is a list of screw sizes for some popular car brands:

Acura

The standard license plate screw size for Acura vehicles is not specified in the source but is likely similar to other popular car brands.

Audi

The standard license plate screw size for Audi vehicles is M6-1.0 x 16mm.

BMW

The standard license plate screw size for BMW vehicles is M4.8 x 16mm. However, screw sizes ranging from 8mm to 12mm will also fit.

Cadillac

The standard license plate screw size for Cadillac vehicles is not specified in the source.

Chevrolet

The standard license plate screw size for Chevrolet vehicles is #14 x 3/4". Screw sizes ranging from 8mm to 12mm will also fit.

Chrysler

The standard license plate screw size for most Chrysler vehicles is 1/4-14x3/4.

Ford

The standard license plate screw size for Ford vehicles is not specified in the source. However, the Ford F-150 truck requires a screw size of 1/4-14-5/8 inch.

General Motors (GM)

The standard license plate screw size for most GM vehicles is #14 1/4" x 3/4".

Honda

The standard license plate screw size for Honda vehicles is M6-1.0 x 20mm or 1/4-14-3/4".

Hyundai

The standard license plate screw size for Hyundai vehicles is not specified in the source.

Jeep

The standard license plate screw size for Jeep vehicles is 1/4-14-3/4".

Kia

The standard license plate screw size for Kia vehicles is M6 x 1.0 x 16-25mm.

Lexus

The standard license plate screw size for Lexus vehicles is 6.3mm x 25mm.

Mazda

For the Mazda 3, the license plate mounting bracket recommends using 6mm or 1/4" self-tapping screws.

Mercedes-Benz

The standard license plate screw size for Mercedes-Benz vehicles is not specified in the source.

Mitsubishi

The standard license plate screw size for most Mitsubishi vehicles is M6 x 1.0 x 10mm. Some models may also use a 16mm extended screw.

Nissan

The standard license plate screw size for Nissan vehicles is 1/4-14-3/4 inches.

Pontiac

The standard license plate screw size for Pontiac vehicles is not specified in the source.

Porsche

The standard license plate screw size for Porsche vehicles is 1/4-14-3/4 inches.

RAM

The standard license plate screw size for RAM trucks is 1/4-14-3/4 inch.

Subaru

The standard license plate screw size for Subaru vehicles is not specified in the source.

Suzuki

The standard license plate screw size for Suzuki vehicles is #14 1/4" x 3/4".

Tesla

The standard license plate screw size for Tesla vehicles is M5-0.8 x 8mm.

Toyota

The standard license plate screw size for Toyota vehicles is M6 1 x 0.5 x 0.5 inches.

Volkswagen

The standard license plate screw size for most Volkswagen vehicles is M6-1.0 x 16mm.

Volvo

The standard license plate screw size for Volvo vehicles is not specified in the source.

It is important to note that some car brands, such as BMW and Chevrolet, may have specific screw size requirements that fall within a range, and others may use Original Equipment Manufacturer (OEM) screws designed specifically for their vehicles. When replacing license plate screws, it is crucial to use the correct screw size and type to ensure a secure fit and avoid damage to your vehicle.

Screw lengths

Screw length is a crucial factor to consider when choosing license plate screws. The correct screw length ensures a secure and stable fit, preventing the license plate from becoming loose during driving. The appropriate screw length also depends on the vehicle's make and model, as well as the material of the license plate and mounting bracket.

For plastic license plates and brackets, shorter screws are typically used since plastic is less rigid. On the other hand, metal license plates and brackets require longer screws that can penetrate the thicker material securely.

When it comes to metric screw sizes, lengths such as 6mm, 8mm, and 16mm are commonly available. For example, M6 screws have a diameter of 6mm and are suitable for most standard vehicles, while M8 screws, with an 8mm diameter, are larger and more robust, often used for heavy-duty applications.

Standard screw sizes are also available, typically measured in inches. A common standard screw length is 1/4-14-3/4 inches, where the last fraction (3/4) indicates the screw length in inches. This size is widely used for license plates in North America and fits most vehicles.

It's important to note that the screw length should match the thickness of the license plate and the depth of the mounting holes. Using screws that are too long or too short can result in an insecure fit or damage to the license plate or vehicle.

When replacing license plate screws, it's recommended to refer to the vehicle's manual or consult a mechanic to ensure the correct screw length and type are used.

Frequently asked questions