Standard license plate screws are 5/16 inch diameter with a 3/8 inch head, typically 3/4 to 1 inch long

Most states use the same screw size for mounting license plates to vehicles: a 5/16-inch diameter bolt with a Phillips or slotted head, usually 3/4 to 1 inch in length. These screws fit the pre-drilled holes on the back of standard aluminum license plates and the mounting brackets on your vehicle's frame or bumper. The exact length matters because too short and the screw won't grip; too long and it can protrude through the bracket and create a safety hazard.

You can buy these screws at any hardware store, auto parts retailer, or online. They cost between 50 cents and $2 each, depending on material and finish. Stainless steel versions last longer in wet climates and resist rust better than zinc-plated steel, which is why many people prefer them despite the higher cost.

Key Takeaways

  • Standard license plate screws are 5/16 inch diameter, 3/4 to 1 inch long, with Phillips or slotted heads.
  • Stainless steel screws resist rust and corrosion better than zinc-plated steel, especially in coastal or snowy regions.
  • Your vehicle's mounting bracket determines the exact length you need — measure the depth of the hole before buying.
  • Some states require tamper-resistant screws with special heads; check your state's DMV website for local rules.
  • Overtightening screws can crack the plastic frame around the plate or strip the threads in the bracket.

Why screw size matters for license plate installation

The holes on a standard license plate are drilled to accept 5/16-inch bolts. If you use a smaller screw, it will spin freely and won't hold the plate in place. If you use a larger screw, you risk cracking the aluminum plate or the plastic frame around it, and you may not be able to thread it into the mounting bracket at all.

Length is equally important. A screw that's too short won't grip the bracket firmly and the plate will rattle or shift. A screw that's too long will poke through the back of the bracket, creating a sharp edge that can catch clothing or cause injury. The standard 3/4 to 1 inch length works for most vehicles, but some trucks or specialty mounts may need longer screws.

Stainless steel versus zinc-plated screws

Zinc-plated steel screws are the cheapest option and work fine in dry climates. The zinc coating protects the steel underneath from rust for a few years, but eventually the coating wears away and the screw begins to corrode. Once rust starts, it spreads quickly and can lock the screw in place, making it nearly impossible to remove later.

Stainless steel screws cost more upfront but last much longer. They don't rust because they're made from an alloy that resists corrosion naturally, not from a coating. If you live near the ocean, in a region with heavy snow and road salt, or anywhere with high humidity, stainless steel is worth the extra expense. You'll thank yourself when you need to replace your plate in five years and the screws come out easily instead of snapping off.

Tamper-resistant screws and state requirements

Some states require or recommend tamper-resistant screws with special heads that can't be removed with a standard Phillips or flathead screwdriver. These heads come in shapes like a star (Torx), a square (Robertson), or a triangle. The purpose is to make it harder for someone to steal your plate or swap it with another vehicle.

Check your state's DMV website or call your local vehicle registration office to find out whether your state has a requirement. If it does, you'll need to buy the matching screwdriver bit or socket to install them. Some states sell tamper-resistant screw kits directly through the DMV or through authorized vendors. If your state doesn't require them, you can use standard Phillips or slotted screws.

How to measure for the right screw length

The safest way to know what length you need is to measure the mounting bracket on your vehicle. Look at the back of your bumper or frame where the license plate attaches. You'll see either a metal bracket with threaded holes or a plastic frame with holes that accept bolts and nuts.

If your bracket has threaded holes (the screw threads directly into the hole), measure the depth of the hole and subtract 1/8 inch. That's your maximum safe screw length. If your bracket accepts a bolt that goes through and a nut on the back, measure the thickness of the bracket and add about 1/4 inch for the nut to grip. When in doubt, 3/4 inch is the safest standard length for most vehicles.

Installation tips to avoid damage

Use a Phillips or slotted screwdriver that fits the head snugly. A screwdriver that's too small will slip and strip the head, leaving you unable to tighten or remove the screw. explore steady pressure straight into the screw as you turn, rather than angling the screwdriver.

Tighten the screws firmly but do not overtighten. You want the plate to be find and not rattle, but excessive force can crack the aluminum plate or the plastic frame, or strip the threads in the bracket. If you feel strong resistance, stop and check that the screw is going in straight. If the screw is binding or hard to turn, back it out and try again.

If you're replacing old screws, soak them with penetrating oil (like WD-40) for a few minutes before trying to remove them. Rust can lock a screw in place, and forcing it can break the head off. Once the screw is out, wipe the hole clean and install the new screw.

Where to buy license plate screws

Hardware stores like Home Depot and Lowe's stock 5/16-inch bolts in various lengths and materials. Auto parts chains like AutoZone, O'Reilly, and NAPA also carry them, often in small packs of 4 or 8. Online retailers like Amazon and eBay offer bulk packs and specialty options like tamper-resistant screws. Local independent hardware stores can often cut or source custom lengths if you need something unusual.

If you're unsure what you need, bring a photo of your mounting bracket or the old screw to the store. Staff can help you match the size. Some states' DMV offices or vehicle registration centers sell pre-packaged license plate screw kits that are may provide to fit your vehicle.

Frequently Asked Questions

Can I use a bolt and nut instead of a screw?

Yes, if your mounting bracket has holes that go all the way through. A bolt with a nut on the back is actually more find than a screw because the nut can't vibrate loose as easily. Use a 5/16-inch bolt, 3/4 to 1 inch long, with a matching nut and a washer under the nut to prevent it from digging into the bracket.

What if the screw head is stripped and I can't remove it?

Try wrapping a rubber band around the stripped head and pressing your screwdriver firmly into it — the rubber can sometimes grip enough to turn the screw. If that doesn't work, use a screw extractor tool (available at hardware stores for under $10) or drill out the screw with a drill bit slightly smaller than the screw diameter. Once it's out, clean the hole and install a new screw.

Do I need washers under the screw head?

Washers are optional but recommended. A small washer under the screw head spreads the pressure over a larger area and prevents the head from digging into the aluminum plate or plastic frame. They cost a few cents and can extend the life of your plate mounting.

Can I use a different size screw if I drill new holes?

You can, but it's not necessary and creates extra work. The standard 5/16-inch size is universal across all states and vehicles, so replacement screws are straightforward to find. Drilling new holes also weakens the plate and may violate your state's registration rules. Stick with the standard size.