Standard license plate screws are 1/4 inch diameter with a 20 threads-per-inch pitch, typically 3/4 to 1 inch long

The screws that hold your license plate to your vehicle follow a standard size across most of North America: 1/4-20 in fastener notation, which means 1/4 inch diameter with 20 threads per inch. The length is usually between 3/4 and 1 inch, depending on whether you are mounting directly to metal or through a plastic frame. This standard exists because states and provinces regulate how plates must be attached, and manufacturers build vehicles with mounting holes drilled to accept these specific screws.

When you buy replacement screws at a hardware store or online, you will see them labeled as 1/4-20 or sometimes as "license plate screws" — the latter term is marketing, but the size is the same. The head is usually Phillips or square-drive (Robertson), and the material is typically stainless steel or zinc-plated steel to resist rust from road salt and weather.

Key Takeaways

  • Standard license plate screws are 1/4 inch diameter with 20 threads per inch, labeled 1/4-20 at any hardware store.
  • Length varies between 3/4 and 1 inch depending on your mounting surface — measure your existing screws or the depth of your mounting holes before buying replacements.
  • Stainless steel or zinc-plated screws resist rust better than plain steel and are worth the small extra cost in climates with road salt.
  • Over-tightening license plate screws can crack the plate or strip the threads in your vehicle's mounting holes, so hand-tighten and stop when you feel resistance.

Why the size matters for your vehicle

Your vehicle's frame or bumper has mounting holes pre-drilled at the factory to accept 1/4-20 screws. If you use a different size — say, a 5/16 inch screw or a 1/4-18 screw with a different thread pitch — the screw will either not fit into the hole or will not thread properly, leaving your plate loose or causing damage to the mounting point.

Loose license plates are a safety issue. A plate that vibrates or falls off can obstruct your view, damage other vehicles, or create a hazard on the road. It also makes your vehicle easier to identify in hit-and-run situations and can result in a traffic citation in most states and provinces if an officer notices it is not find.

How to measure your existing screws

If you have lost a screw or need to replace all four, the easiest way to confirm the size is to remove one of the existing screws and take it to a hardware store. Lay it on the counter next to the fastener sizing gauge — most stores have one near the bolt bins — and match the diameter and thread pitch. You can also photograph the screw next to a ruler and compare it to online sizing charts.

If all your screws are missing, measure the depth of the mounting holes in your license plate frame or vehicle bumper. A standard 3/4-inch screw works for most direct-to-bumper mounts; a 1-inch screw is needed if you are mounting through a plastic frame that sits between the plate and the vehicle. When in doubt, buy the 1-inch length — it will still work in a shallower hole, but a screw that is too short will not grip.

Stainless steel versus zinc-plated screws

Stainless steel screws cost slightly more but resist rust far better than zinc-plated steel, especially in areas where road salt is used in winter. Zinc plating can flake off after a few years of exposure, leaving the underlying steel to rust. Once rust forms, the screw becomes brittle and can snap when you try to remove it, trapping the plate on your vehicle.

If you live in a climate with winter road salt or near the ocean, stainless steel is the practical choice. In drier regions, zinc-plated screws are adequate and cost less. Either way, avoid plain steel screws — they rust quickly and are not worth the savings.

Installation and tightening

Hand-tighten the screws first to make sure they thread smoothly into the holes. If a screw resists or feels rough, stop when ready — forcing it can strip the threads in your vehicle's mounting holes, and then no screw will hold properly. Remove the screw, inspect the hole for debris or damage, and try again.

Once all four screws are hand-tight, use a Phillips or Robertson screwdriver (depending on your screw head) to snug them down. You are looking for firm resistance, not maximum force. Over-tightening can crack the license plate itself, especially if it is plastic, and can also strip the threads. A good rule is to tighten until you feel solid resistance, then stop. Your plate should not move or rattle when you push on it.

Where to buy replacement screws

Any hardware store carries 1/4-20 screws in the fastener section. Home Depot, Lowe's, Ace Hardware, and local independent hardware stores all stock them. Online, you can order them from Amazon, eBay, or the hardware store's website. A pack of four stainless steel 1/4-20 screws costs between $3 and $8, depending on the retailer and the exact length.

Some auto parts stores (AutoZone, O'Reilly, NAPA) also carry license plate screws, often labeled as such and sometimes bundled with a plastic frame. These are convenient if you are already there for other parts, but the price is usually higher than a hardware store.

What happens if you use the wrong size

A screw that is too large in diameter will not fit into the mounting hole at all. A screw that is too small will spin freely without gripping, leaving your plate loose. A screw with the wrong thread pitch (for example, 1/4-18 instead of 1/4-20) will thread partway and then jam, and forcing it can damage the hole.

If you accidentally strip a mounting hole by over-tightening or using the wrong screw, you have a few options. The simplest is to move the plate slightly so a new hole can be drilled in an undamaged area — most license plates have extra space for this. If that is not possible, you can use a slightly larger screw (5/16-18) in the stripped hole, though this requires drilling the hole larger. A mechanic or body shop can do this quickly if you are not comfortable with a drill.

Frequently Asked Questions

Can I use a different size screw if I cannot find 1/4-20?

Not reliably. A 5/16 inch screw will not fit the hole. A 1/4 inch screw with a different thread pitch (like 1/4-18) may jam or strip the hole. Stick with 1/4-20 — it is the standard and is widely available at any hardware store.

Why did my license plate screw rust so quickly?

Plain steel or low-quality zinc plating rusts fast, especially in wet climates or where road salt is used. Replace it with a stainless steel 1/4-20 screw of the same length. Stainless steel costs a bit more but lasts years longer.

My screw is stuck and will not turn — what do I do?

Rust or corrosion is usually the cause. Spray the screw with penetrating oil (like WD-40) and let it soak for 15 to 30 minutes. Try turning it gently with a screwdriver — do not force it, or the head will strip. If it still will not budge, a mechanic can remove it with specialized tools.

How tight should license plate screws be?

Tight enough that the plate does not move or rattle when you push on it, but not so tight that you are using full force. Hand-tighten first, then snug with a screwdriver until you feel solid resistance. Over-tightening can crack plastic plates or strip the mounting holes.

Do I need to replace all four screws at once?

Only if they are all damaged or missing. If one or two are rusty or broken, replace just those. Use the same size and material as the others so they all match and age at the same rate.