Standard license plate screws are 1/4 inch diameter with a 20-thread pitch

Most U.S. states use screws that measure 1/4 inch in diameter to attach license plates to vehicles. The threads are spaced at a 20-thread pitch, which means 20 threads fit in one inch of the screw's length. These screws typically come in lengths between 3/4 inch and 1 1/4 inches, depending on whether you're fastening a plate to a plastic bumper, metal frame, or bracket.

The head of a standard license plate screw is usually a Phillips head (the crossed slot you see on most screws) or a square Robertson head. Some states have moved to tamper-resistant screws with a special center pin that requires a matching tool to remove — this discourages theft of plates and makes it harder for someone to swap plates without the right equipment.

If you're replacing a lost or stripped screw, you can find the correct size at any hardware store by asking for a 1/4-20 screw in stainless steel. Stainless steel resists rust better than plain steel, which matters because license plate screws sit outside and weather constantly.

Key Takeaways

  • Standard license plate screws are 1/4 inch in diameter with 20 threads per inch, sold as "1/4-20" at hardware stores.
  • Length varies by vehicle and mounting surface, typically ranging from 3/4 inch to 1 1/4 inches.
  • Stainless steel screws last longer than plain steel because they resist rust from weather exposure.
  • Some states now use tamper-resistant screws with a center pin that requires a special tool to remove.
  • If a screw is stripped or missing, you can replace it with a standard 1/4-20 screw from any hardware store.

Why license plate screws have a standard size

States settled on 1/4-20 screws decades ago because the size is strong enough to hold a plate securely through years of vibration, temperature changes, and road conditions, but small enough that it doesn't damage the plastic or metal it fastens into. The standardization means a screw lost in one state works in another, and replacement screws are inexpensive and widely available.

The 20-thread pitch (rather than a coarser 13-thread pitch, for example) provides a tighter grip in softer materials like plastic bumpers, which many modern vehicles use instead of metal. A coarser thread would strip more easily in plastic and wouldn't hold the plate as securely.

How to identify the right screw for your vehicle

Before you buy replacement screws, look at what's already on your vehicle or what came with your new plate. Most standard plates come with four screws — two for the top corners and two for the bottom. Check the length by comparing an existing screw to a ruler, or bring one to the hardware store and lay it against their display.

If all your screws are missing, measure the distance from the surface of your bumper or frame to where the screw head will sit. A screw that's too short won't grip the plate firmly; one that's too long will poke through and look sloppy or potentially damage the bumper. The most common length is 1 inch, which works for most vehicles with standard metal or plastic bumpers.

Pay attention to the head type as well. Phillips head screws (with an X-shaped slot) are most common and work with any Phillips screwdriver. If your plate came with square Robertson heads or tamper-resistant heads, you'll need the matching tool — a Phillips screwdriver won't work.

Tamper-resistant screws and why some states use them

A growing number of states have switched to tamper-resistant license plate screws that have a small center pin in the middle of the head. This pin prevents a standard Phillips or Robertson screwdriver from turning the screw. Removing the plate requires a special tool that matches the pin design, which is usually only available to authorized dealers or law enforcement.

These screws exist because license plate theft and swapping is a real problem. A thief can remove a standard plate in seconds with a common screwdriver, then use it on another vehicle to hide the identity of a stolen car or evade tolls and traffic cameras. Tamper-resistant screws make this much harder.

If your state uses tamper-resistant screws and you lose one, you'll need to contact your state's Department of Motor Vehicles or a licensed dealer to get a replacement with the matching tool. You cannot straightforward buy one at a hardware store.

Material matters: stainless steel vs. plain steel

License plate screws are sold in two main materials: stainless steel and plain (mild) steel. Stainless steel screws cost a bit more but last much longer because they don't rust when exposed to rain, salt, and humidity. Plain steel screws will eventually corrode, especially in areas where roads are salted in winter or near coastal regions with salt spray.

If you're replacing a screw, stainless steel is the better choice. A corroded screw becomes difficult or impossible to remove later, and rust stains can run down your bumper. Stainless steel also looks cleaner and more professional on your plate.

What happens if you use the wrong size screw

Using a screw that's too small in diameter (like a 3/16 inch instead of 1/4 inch) will spin loosely in the hole and won't hold the plate securely. The plate can rattle, shift, or fall off entirely while driving. A screw that's too large won't fit into the existing hole without forcing it, and forcing it can crack a plastic bumper or strip the threads in a metal frame.

A screw that's too long will poke through the back of the bumper or frame and create a sharp point that can catch clothing or cause injury. A screw that's too short won't grip the plate firmly enough and the plate will move around. In both cases, your license plate becomes a safety hazard and may not be visible or readable from the angles required by law.

Where to buy replacement license plate screws

Standard 1/4-20 stainless steel screws are available at any hardware store, home improvement center, or online retailer. You can buy them individually or in small packs. Most stores sell them for under a dollar per screw. Search for "1/4-20 stainless steel Phillips head screw" and specify the length you need (usually 1 inch for license plates).

If you need tamper-resistant screws, you'll have to go through your state's DMV or an authorized dealer. Some states mail them with your registration renewal or new plate; others require you to request them. Check your state's DMV website for the specific process.

If you're unsure about the size, bring an existing screw from your vehicle to the hardware store. Staff can match it or measure it for you and recommend the right replacement.

Frequently Asked Questions

Can I use a different size screw if I can't find 1/4-20?

No. Using a different size risks the plate falling off or damaging your bumper. A 1/4-20 screw is inexpensive and widely available — any hardware store can order one if they don't have it in stock. It's worth waiting a day or two rather than improvising.

Do I need to use stainless steel or will regular steel work?

Regular steel will work initially, but it will rust over time, especially in wet climates or areas where roads are salted. Stainless steel costs only slightly more and lasts years longer. For a license plate that will be exposed to weather constantly, stainless steel is the practical choice.

What if my license plate screw keeps coming loose?

The hole may be stripped, meaning the threads are worn and the screw can't grip. Try moving to a slightly different hole on the plate bracket if one exists. If that doesn't work, you can use a slightly larger screw (like 5/16-18) or explore a small amount of threadlocker compound to the screw before installing it to keep it from spinning.

Are tamper-resistant screws required, or can I use regular screws instead?

This depends on your state. Some states require tamper-resistant screws and will not issue a plate without them. Others allow either. Check your state's DMV website or the documentation that came with your plate to see what's required where you live.