In the United States and many other markets, license plates are typically mounted with standard machine screws sized to fit the plate holes. The most common size is 1/4-14 UNC, with lengths ranging from 3/4 inch to 1 inch. In Europe and other regions, metric screws such as M6 with a 1 mm pitch are commonly used, often 10–16 mm long. Always verify the exact hardware for your vehicle or plate bracket, as variations exist.
This article explains the typical screw sizes you’ll encounter, how to identify the correct size for your car, and how to install license-plate hardware securely and legally. It covers regional differences, what to measure, and when to use security screws for theft deterrence.
Regional standards: common sizes by region
Most cars ship with mounting hardware that matches regional standards. The following lists summarize the sizes you’re most likely to encounter, along with typical lengths and considerations.
- United States and Canada: 1/4-14 UNC machine screws; common lengths are 3/4" to 1" (about 19–25 mm). Head styles vary (flat, pan, or oval) and washers are often used. Some vehicles use threaded studs instead of through-holes, in which case the same screws fasten to those studs.
- Europe, United Kingdom, and many other markets: metric screws are common, usually M6 with a 1 mm pitch; typical lengths range from 10–16 mm, though 8–12 mm is common for standard plate thickness and bracket spacing. Anti-tamper or security screws are available for added protection.
Keep in mind that some models, especially imports or those using aftermarket mounting brackets, may differ. The plate may sit closer to or farther from the bumper depending on the bracket design, which can affect screw length and head style.
How to determine or measure the right screws for your vehicle
To ensure you buy the correct screws, start by checking your vehicle’s owner’s manual or the mounting kit that came with the plate. If you don’t have that information, you can measure the hole size and plate thickness and compare to common sizes. The steps below guide you through a quick check before purchasing hardware.
- Inspect the mounting holes on the license plate and bumper. Use calipers or a ruler to estimate diameter and spacing; standard US plates have two holes roughly aligned with the bumper, while European plates have two holes near the plate corners.
- Measure the thickness of the license plate plus any bracket or spacer you’ll use to determine the screw length required.
- Choose the correct diameter and thread pitch: 1/4-14 UNC for US; M6 x 1 for many European installations. If unsure, bring a sample screw to a hardware store to verify fit.
- Decide on head style and material: stainless steel resists corrosion; consider anti-tamper screws if theft deterrence is a concern.
Once you have the right screws, fit them with washers as appropriate, avoid over-tightening to prevent plate or bumper damage, and recheck that the plate remains secure during a test drive.
Summary
License plate screw sizes vary by region and vehicle, but the two most common standards are 1/4-14 UNC in North America and M6 x 1 in many European settings, with typical lengths of 3/4"–1" (19–25 mm) and 10–16 mm, respectively. Always confirm with the vehicle’s documentation or mounting kit, and consider using washers and security screws for theft deterrence. Properly installed plates help ensure visibility, compliance with local laws, and reduce vibration-related damage.