Standard License Plate Screw Sizes in the United States

License plate screws in the United States are almost always 5/16 inch diameter with a 1 1/4 inch length. These are the screws that hold your plate to the mounting bracket on your vehicle. The head is typically Phillips or slotted, and the screw itself is usually stainless steel to resist rust and corrosion from road salt and weather.

Some states and some vehicles use slightly different specifications. A few regions use metric screws (8mm diameter), and some specialty vehicles or custom brackets may call for different lengths. If you are replacing screws on a newer vehicle, check your owner's manual or the bracket itself before buying — the information is often printed on the bracket or in the documentation that came with it.

The reason 5/16 inch became standard is practical: it is large enough to hold a plate securely without stripping easily, but small enough that the holes in most license plates and brackets align with it. If you lose a screw or one rusts through, you can buy a replacement set at any hardware store for a few dollars.

Key Takeaways

  • Standard U.S. license plate screws are 5/16 inch diameter and 1 1/4 inch long, usually stainless steel with Phillips or slotted heads.
  • Some states and vehicles use metric 8mm screws instead, so check your bracket or owner's manual before replacing.
  • Stainless steel screws resist rust better than galvanized or plain steel, especially in areas with road salt.
  • Replacement screws are inexpensive and widely available at hardware stores, auto parts shops, and online retailers.

How to Identify Your Screw Size

If you have a screw that came loose or broke, the easiest way to identify the size is to take it to a hardware store and match it against their screw display. Bring the old screw with you if you still have it. If you do not have the screw, measure the diameter of the hole in your license plate with a ruler or caliper — it should be just over 5/16 inch (about 8mm).

You can also check your vehicle's owner's manual or contact your state's Department of Motor Vehicles. Many states publish the specifications for their plates online. If your vehicle is newer, the dealership can tell you the exact screw size used on that model.

Stainless Steel vs. Other Materials

Stainless steel is the best choice for license plate screws because it does not rust, even when exposed to salt, moisture, and temperature swings. Galvanized steel (zinc-coated) is cheaper and works in dry climates, but it will eventually rust in areas that use road salt or have high humidity. Plain steel screws rust quickly and should be avoided.

If you live near the ocean, in a snowy region, or anywhere road salt is used, spend the extra dollar or two on stainless steel. The screw will last the life of your vehicle instead of needing replacement every few years. Stainless steel also looks cleaner and more finished, which matters if your plate is visible and you care about appearance.

Where to Buy Replacement Screws

Replacement license plate screws are sold at hardware stores (Home Depot, Lowe's, Ace Hardware), auto parts retailers (AutoZone, O'Reilly, NAPA), and online through Amazon, eBay, or specialty fastener sites. A pack of four stainless steel 5/16-inch by 1 1/4-inch screws typically costs between $3 and $8.

Many auto parts stores will also sell them individually if you only need one or two. If you are unsure of the size, bring your old screw or your license plate with you so the staff can match it. Some stores will do this matching for free.

Installing New License Plate Screws

Remove the old screw by turning it counterclockwise with a Phillips or flathead screwdriver, depending on the head type. If the screw is rusted and stuck, spray it with penetrating oil (like WD-40) and wait 10 to 15 minutes before trying again. Do not force it — you can strip the hole in the plate or bracket.

Once the old screw is out, insert the new one and turn it clockwise until it is snug. Do not overtighten — you only need enough pressure to hold the plate firmly in place. Overtightening can crack the plate or strip the hole. If you are installing all four screws, tighten them in an X pattern (top-left, bottom-right, top-right, bottom-left) so the plate sits evenly.

Common Mistakes to Avoid

The most common mistake is buying the wrong size. Always check your bracket or bring your old screw to the store. Another mistake is using plain steel or galvanized screws in a climate where they will rust — stainless steel costs only slightly more and lasts much longer.

Overtightening is also common. You do not need to crank the screw down hard. If the plate moves when you push it, tighten a bit more, but stop as soon as it is solid. Stripping the hole in a plastic bracket or cracking a metal plate is expensive to fix and easily avoided by using moderate pressure.

Finally, do not ignore a missing or loose screw. A plate that is hanging by one or two screws can fall off on the highway, which is both a safety hazard and illegal in most states. Replace missing screws as soon as you notice them.

Frequently Asked Questions

Can I use a different size screw if I cannot find 5/16 inch?

Not safely. Using a screw that is too small will not hold the plate securely, and one that is too large may not fit through the holes or could crack the plate. Stick with 5/16 inch unless your manual or bracket specifically calls for something else. Hardware stores stock this size widely, so finding it is not difficult.

Do I need to replace all four screws at once?

No. You can replace one or two screws if only those are damaged or missing. However, if multiple screws are rusted, it is often worth replacing all four at the same time so they all match and age at the same rate.

What if the hole in my plate is stripped and the screw will not tighten?

You can use a slightly larger screw (like 3/8 inch) if the hole is only slightly enlarged, but this is not ideal. A better solution is to buy a new license plate from your state's DMV — they are inexpensive and come with new holes. Alternatively, some people use a rubber washer under the screw head to grip a slightly enlarged hole, though this is temporary.

Are metric screws (8mm) compatible with standard U.S. plates?

Not usually. Metric 8mm screws are slightly larger than 5/16 inch and will not fit standard U.S. license plate holes. Some newer vehicles or imported cars may use metric screws, but most domestic vehicles use the 5/16-inch standard. Check your bracket or manual to be sure.

Can I use a power drill to install license plate screws?

You can, but use a low speed and stop as soon as the screw is snug. A power drill makes it straightforward to overtighten without realizing it, which can strip the hole or crack the plate. A hand screwdriver gives you better control and feel for when to stop.