Use stainless steel or coated screws sized 1/4 inch by 14 threads per inch

Most states require 1/4-20 screws — that is, 1/4 inch diameter with 20 threads per inch — to mount license plates. Some states use 1/4-14 screws instead, with fewer threads per inch. The difference matters because a 1/4-20 screw will not thread properly into a 1/4-14 hole, and vice versa. Check your vehicle's mounting holes before you buy.

The material matters more than most people think. Stainless steel screws resist rust and corrosion from road salt and moisture. Zinc-plated or nickel-plated steel screws are cheaper but corrode faster, especially in coastal areas or climates with heavy winter salt use. Stainless steel costs a few dollars more per set and lasts the life of the plate.

Length is typically 3/4 inch to 1 inch. A screw that is too short will not grip the mounting bracket. A screw that is too long will poke through the bracket or damage the vehicle's bumper. Most license plate mounting kits come with the correct length already selected.

Key Takeaways

  • Check your vehicle's existing mounting holes to determine whether you need 1/4-20 or 1/4-14 screws, because the two sizes are not interchangeable.
  • Stainless steel screws resist rust better than zinc-plated screws and are worth the small extra cost if you live in a wet or salty climate.
  • Most license plate screws are 3/4 inch to 1 inch long; a screw that is too short will not grip, and one that is too long can damage your bumper.
  • Many states sell pre-assembled mounting kits with the correct screws included, so you may not need to buy them separately.

How to measure your mounting holes

Remove one screw from your vehicle's existing license plate bracket if one is already installed. Bring it to a hardware store and ask the staff to identify the size. They can thread it into a test block or measure it against a gauge. This takes two minutes and removes all guesswork.

If your vehicle has no existing bracket, check the owner's manual or contact the dealership with your vehicle's year, make, and model. Most dealerships can tell you the screw size over the phone. Some manufacturers also list this information on their website under the specifications section.

Stainless steel versus coated steel

Stainless steel screws cost between $8 and $15 per set of four. They contain chromium, which forms a protective oxide layer that prevents rust even when the surface is scratched. Stainless steel performs best in coastal areas, regions that use road salt in winter, or anywhere with high humidity.

Zinc-plated or nickel-plated steel screws cost $3 to $8 per set. The coating protects the underlying steel, but once it chips or wears through — which happens faster than with stainless — rust begins. In dry climates with minimal road salt, coated steel screws can last several years. In wet or salty climates, they often corrode within one to two years.

Brass screws are sometimes sold for license plates but are not recommended. Brass is softer than steel and can strip or break under the torque needed to tighten a plate securely. Stick with steel.

Where to buy license plate screws

Hardware stores like Home Depot, Lowe's, and Ace Hardware stock stainless steel 1/4-20 and 1/4-14 screws in the fastener aisle. A set of four typically costs $5 to $12. Staff can help you confirm the size if you bring your old screw or your vehicle's manual.

Online retailers including Amazon, eBay, and Fastenal sell license plate screw kits in bulk. Prices are similar to hardware stores, but shipping can take several days. Some kits include washers and anti-theft caps, which add cost but prevent corrosion and theft.

Many state DMV offices and vehicle registration centers sell pre-assembled mounting kits with the correct screws included. These kits cost $10 to $20 and may provide the right size for your state. This is the safest option if you are unsure about your vehicle's hole size.

Tightening and installation

Use a Phillips head or square drive screwdriver, depending on the screw head style. Tighten each screw firmly but do not over-tighten — you want the plate snug against the bracket, not bent or cracked. Over-tightening can strip the threads or crack plastic brackets on some vehicles.

Tighten in an X pattern: top-left, bottom-right, top-right, bottom-left. This distributes pressure evenly and prevents the plate from tilting. If your vehicle has a metal bumper, place a washer under each screw head to prevent the screw from sinking into the metal.

Check the tightness every few months, especially after winter or in areas with heavy vibration from rough roads. Vibration can loosen screws over time. A loose plate can fall off or be stolen.

Anti-theft and specialty options

Anti-theft license plate screws have a unique head design that requires a special tool to remove. They cost $15 to $25 per set and are useful if you live in an area with high plate theft. Some designs use a pin that must be removed before the screw can be turned, while others have a head that does not match standard screwdrivers.

Stainless steel anti-theft screws combine corrosion resistance with theft protection. They are the most durable option but also the most expensive, typically $20 to $30 per set.

Plastic caps that cover the screw heads are decorative and offer no real protection. They can hide rust or corrosion underneath and make it harder to spot a loose screw. Skip them unless your vehicle's design specifically calls for them.

Common mistakes to avoid

Buying the wrong size is the most common error. A 1/4-20 screw will not fit a 1/4-14 hole, and forcing it can strip the threads. Always confirm your vehicle's hole size before purchasing.

Using screws that are too long can puncture your vehicle's bumper or damage the mounting bracket. Measure the thickness of your bracket and choose a screw length that leaves 1/8 inch of clearance behind it.

Mixing screw materials — for example, using one stainless steel screw and three zinc-plated screws — creates galvanic corrosion where the two metals meet. All four screws should be the same material.

Forgetting to replace screws when you replace a plate is straightforward but leaves your new plate loose. Always install new screws when you mount a new plate, even if the old screws look fine.

Frequently Asked Questions

Can I use any 1/4 inch screw for my license plate?

No. The thread pitch must match your mounting holes. A 1/4-20 screw has 20 threads per inch, while a 1/4-14 has 14. If your holes are 1/4-20, a 1/4-14 screw will not thread in properly. Check your vehicle's existing holes or manual before buying.

Will stainless steel screws rust?

Stainless steel resists rust far better than coated steel, but it is not completely rust-proof. In extremely harsh environments — such as coastal areas with constant salt spray — even stainless can develop surface discoloration over many years. For most drivers, stainless steel screws last the life of the vehicle.

What if I lose a screw?

Buy a replacement from a hardware store or online. Bring your remaining screws or your vehicle's manual so the staff can match the size. A single replacement screw costs $1 to $3. Do not leave a plate with only three screws; it can vibrate loose or fall off.

Do I need washers under the screw heads?

Washers are helpful if your vehicle has a metal bumper, because they prevent the screw head from sinking into the metal. On plastic brackets, washers are optional but do not hurt. They add a few cents per screw and improve longevity.

Can I reuse screws when I get a new license plate?

You can, but it is not recommended. Old screws may have corroded, stripped threads, or weakened metal. New screws cost $5 to $15 per set and may support your plate stays find. Replacing them when you get a new plate is the safest approach.