I remember a few years back, wrestling with a new bumper on my old truck. The old screws had rusted solid, and I just wanted to slap the new one on and be done with it. I figured, ‘How hard can it be? License plate screws gotta be a standard size, right?’ Wrong. I ended up making three trips to the hardware store, buying a whole mess of different sizes, before I finally found the right ones. It was a frustrating afternoon that taught me a valuable lesson: not everything that looks simple actually is.
So, are license plate screws a standard size? The short answer is yes, but with enough caveats to make your head spin if you’re not careful. Let’s break down what that actually means and how to avoid my expensive trip to the screw aisle.
The Big Screw-Up: Why ‘standard’ Isn’t Always Standard
Look, I’ve spent more hours than I care to admit fiddling with car parts, from simple bolt replacements to full engine swaps. You develop a sense for what’s common.
Most things in the automotive world have some sort of convention. But license plate screws? They’re a bit of a wild west.
The common advice you’ll find online is that they’re usually a #14 or 5/16-inch screw. And yeah, often that’s true. But I’ve pulled screws out of vehicles that were definitely NOT that size.
I’ve seen anything from a #10 all the way up to a 3/8-inch bolt, with all sorts of thread pitches in between. It’s maddening when you just need to get the job done and you’re staring at a gaping hole where your plate used to be.
My personal worst was a classic muscle car. The owner insisted on original parts, which meant I had to track down some obscure, possibly metric-adjacent screw that looked vaguely right. It took weeks.
The problem is, manufacturers have a little wiggle room. They can choose a slightly different thread diameter or length depending on the material of the mounting bracket, the desired strength, or even just what was cheapest in bulk that month. And then there’s the rust factor.
Over time, those holes can get a bit wallowed out, making a ‘standard’ screw fit loosely. So, while you can often get away with the common sizes, expecting a universal fit is a recipe for a headache. Trust me, I’ve been there, and buying a mixed pack of stainless steel screws is cheaper than three trips to Home Depot.
Common Pitfalls and What to Watch Out For
One of the biggest mistakes people make is assuming the screw holding the old plate on is the correct size. If it’s rusted, stripped, or just jammed in there, it might be the wrong size and just barely holding on. Or maybe it was replaced with a non-standard screw years ago. Another common error is not considering the length.
Too short, and your plate is flapping in the wind. Too long, and you’re drilling into something you shouldn’t be, like a wiring harness or, worse, a fuel line. (See Also: Can I Use Galvanized Deck Screws Instead Of Stainless Steel )
I once had a screw that was just a quarter-inch too long on a rear bumper, and it ended up poking into the trunk floor. Not a disaster, but definitely annoying to fix.
Then there’s the material. People often grab zinc-plated steel screws because they’re cheap. But if you live anywhere with salt on the roads, or just a lot of humidity, those things will rust faster than you can say ‘new plate.’ Stainless steel is almost always the way to go for outdoor automotive applications, even though it costs a bit more upfront.
It’ll save you the hassle of dealing with rusted-out screws again down the line. Finally, don’t forget about the washers. Sometimes the hole in the license plate or the mounting bracket is a bit oversized, and a washer helps distribute the pressure and prevent the screw head from pulling through. A nylon washer can also help prevent metal-on-metal contact, which is good for preventing corrosion.
The Actual Sizes: What You’re Likely to Find
Okay, let’s get down to brass tacks. When we talk about license plate screws, we’re usually talking about two main characteristics: diameter and thread count (or thread pitch). The most common diameter you’ll encounter is the #14 size, which is roughly equivalent to 5/16 of an inch. These are pretty beefy screws, and they’re what you’ll find on a lot of domestic vehicles. They have a coarse thread that bites well into metal and plastic.
However, it’s not unheard of to find #10 screws, which are a bit smaller (about 3/16 of an inch). These are often used on older vehicles or in situations where the mounting holes are smaller. On the metric side of things, you might run into M6 or M8 bolts.
An M6 is roughly 1/4 inch in diameter, and an M8 is about 5/16 inch. The key difference with metric is the thread pitch. While SAE screws often have a coarse thread, metric screws can have fine or coarse threads, and the specific pitch matters for a good fit.
If you’re dealing with a foreign car, or even some newer domestic models, you might need to be prepared for metric sizes. I’ve had to use M6 screws with a fine thread on a European SUV, and it was a specific size that wasn’t readily available at my local corner hardware store. You might need to check with your car’s manual or a specialized auto parts supplier.
Here’s a quick rundown of what you might encounter. Remember, this is a generalization, and your mileage may vary.
| Common Size (SAE) | Approximate Diameter | Common Use | Verdict |
|---|---|---|---|
| #10 | ~3/16 inch | Older vehicles, smaller mounting holes | Good for lighter duty, but can strip easily if over-tightened. |
| #14 | ~5/16 inch | Most common on domestic vehicles | The go-to size for many, generally solid. |
| M6 (Metric) | ~1/4 inch | Many foreign vehicles, some domestic | Make sure you match thread pitch (coarse/fine). |
| M8 (Metric) | ~5/16 inch | Heavier duty applications, some foreign/domestic | Can be similar to #14 SAE, but thread pitch is important. |
The Stainless Steel Argument: Worth the Extra Bucks?
I’ll be blunt: if you live anywhere that sees snow, rain, or even just a lot of humidity, you absolutely should be using stainless steel license plate screws. The few extra dollars you spend upfront are saved tenfold in time and frustration. I’ve had to drill out rusted-in-place screws so many times that I now preemptively buy stainless. It’s not just about looks, although rusty screws look like garbage.
It’s about functionality. When a screw is rusted solid, it can become a nightmare to remove. (See Also: Can Machine Screws Be Used In Wood )
You risk damaging the mounting bracket, the bumper, or even the license plate itself. I once spent over an hour on a single rusted screw with penetrating oil, heat, and a prayer. It was not a good time.
Stainless steel resists corrosion far better than standard zinc-plated or even black oxide screws. While it might not be completely immune to rust in extremely harsh environments over many years, it’s leagues ahead. For a component that’s constantly exposed to the elements, it’s a no-brainer. Most hardware stores will have stainless steel options in the common sizes, often with different head types too – Phillips, Torx, or even Allen heads if you want something a bit more secure or less prone to stripping.
When ‘standard’ Goes Out the Window: Metric and Beyond
Now, let’s talk about the metric menace. While many American cars and trucks stick to SAE (Society of Automotive Engineers) standards, a massive chunk of the vehicles on the road are imports, and even some domestic manufacturers have adopted metric fasteners on certain models. This means you might encounter screws with metric thread sizes. The most common ones you’ll see for license plates are M6 and M8. An M6 screw has a nominal diameter of 6 millimeters (about 1/4 inch) and often comes with a thread pitch of 1.0 mm (fine thread) or 1.25 mm (coarse thread). An M8 screw is 8 millimeters in diameter (about 5/16 inch) and typically has a 1.25 mm or 1.5 mm thread pitch.
The important part here is the thread pitch. Even if the diameter seems right, a mismatched thread pitch will mean the screw won’t engage properly, or worse, it could cross-thread and damage the hole.
My first encounter with this was on a friend’s older Volvo. The plate was held on with what looked like a standard bolt, but the threads were incredibly fine.
We ended up stripping the hole trying to force a regular coarse-thread screw into it. The lesson learned: if you’re unsure, especially with a non-domestic vehicle, it’s worth doing a little homework. A quick search for ‘[your car make and model] license plate screw size’ can often save you a lot of grief. Failing that, taking a trip to an auto parts store that specializes in imports or has a wide selection of fasteners is your best bet.
A Contrarian Take: Don’t Always Trust the Kit
Everyone and their dog will tell you to just buy a ‘license plate screw kit’ from the auto parts store. And yeah, sometimes those kits are fine. They usually come with a variety of common SAE and metric sizes, and a few different types of nuts and washers. But here’s my honest opinion: I’ve wasted money on those kits more times than I can count. Why? Because they invariably include a bunch of sizes I’ll never use, and they often skimp on quality. The screws are usually cheap, zinc-plated steel that will rust within a year. The nuts might be flimsy, and the plastic washers crack after a season.
My contrarian advice is this: identify the exact size and type of screw you need for your vehicle, and then buy individual, high-quality stainless steel screws and appropriate washers/nuts if needed. Yes, it might cost a little more upfront for a few premium screws than a cheap multipack, but you’ll end up with a far more durable and reliable installation. You avoid the frustration of sorting through a dozen incorrect sizes, and you get fasteners that will actually last.
For my personal vehicles, I’ve even gone with security screws that require a special bit to remove. It’s a bit of overkill for most people, but it stops casual theft and gives me peace of mind. The cheap kits are a gamble; buying specific, quality parts is an investment.
Practical Tips for Getting It Right the First Time
So, how do you avoid the screw-buying merry-go-round? Here’s what I’ve learned works. First, if your old screws are still in place and reasonably intact, carefully remove one and take it with you to the hardware store. Even if it’s a bit rusty, you can usually identify the thread size and pitch by eye or by comparing it to known sizes. If they’re completely shot, or you’re dealing with a new plate and bracket, the best approach is to measure the mounting hole diameter and then test-fit screws. Many hardware stores have display boards with different thread sizes where you can try screwing in a bolt to see if it catches. (See Also: Can I Use Wood Screws For Durock )
When you get the screws home, always test-fit them before you fully tighten them down, especially on the final installation. Make sure they thread in smoothly without excessive force. If you have to crank on it hard, it’s probably the wrong thread pitch or size, and you risk cross-threading and damaging the hole. Use a washer, especially if the mounting hole is a bit worn or oversized. A nylon washer can help create a tighter seal and prevent metal-on-metal contact. And, as I’ve hammered home, for anything that lives outside, strongly consider stainless steel. It’s just a better material for the job. If you’re mounting a plate to a painted bumper, a plastic washer can also prevent paint chipping.
The Faq: Quick Answers to Your Burning Questions
What Is the Standard Size for License Plate Screws?
The most common size is a #14 screw, which is approximately 5/16 inch in diameter with a coarse thread. However, you’ll also frequently encounter #10 screws (about 3/16 inch) and metric sizes like M6 (approx. 1/4 inch) and M8 (approx. 5/16 inch), especially on imported vehicles. Thread pitch is also important, particularly with metric sizes, as it dictates how the screw engages with the threads.
Can I Use Any Screws for My License Plate?
While you can technically use almost any screw that fits, it’s not recommended. Using the wrong size or thread pitch can damage your vehicle’s mounting holes. Furthermore, standard steel screws will rust quickly outdoors, leading to difficulty in removal and a generally unsightly appearance. It’s best to use fasteners specifically designed for automotive exterior use, ideally stainless steel.
What’s the Difference Between Sae and Metric License Plate Screws?
SAE screws use imperial measurements (inches and fractions of an inch) for diameter and thread count (threads per inch). Metric screws use millimeters for diameter and a specific thread pitch (millimeters per thread). Even if the diameter seems similar, an SAE screw will not properly thread into a metric hole, and vice versa, unless they are exceptionally close and fortuitously compatible, which is rare.
How Do I Know If My License Plate Screws Are Standard?
The best way is to remove one of your existing screws and compare it to known sizes at a hardware store or auto parts store. You can also look up your specific vehicle make, model, and year online, as many forums and parts suppliers will list the correct fastener sizes. If you’re unsure, purchasing a multi-size kit can be a starting point, but be prepared to select the correct size from the assortment.
Do I Need Special Tools to Install License Plate Screws?
Typically, no. Most license plate screws use standard Phillips head or flathead drivers. Some higher-security options might use Torx or other specialty heads, requiring a corresponding driver bit. If you opt for security screws, make sure you have the correct tool to install and remove them, as this is their primary purpose.
A Word on Security and Anti-Theft Measures
Beyond just getting the right size, you might want to think about security. It’s surprisingly easy for someone to just unscrew your license plate. While it might seem like a minor inconvenience, stolen plates can be used in crimes, causing you a whole lot of headaches with law enforcement. To combat this, there are security license plate screws available. These often have unique head types, like Torx Security (with a pin in the center) or even specialized Allen heads, that require a specific tool to remove. You can usually find these in stainless steel too, so you get the best of both worlds: security and durability.
I’ve installed these on a few cars, and while they add a few minutes to installation, the peace of mind is worth it. You can buy kits that come with the screws and the special tool. Just make sure you keep that tool somewhere safe! If you lose it, you’ll be in the same boat as if you had a rusted screw – you’ll need to drill it out. For most people, standard stainless steel screws are perfectly fine, but if you’re parking your car in a less-than-ideal area, or if you’ve just got a plate you really don’t want to see disappear, security screws are a smart move.
Conclusion
So, are license plate screws a standard size? Mostly, yes, but that ‘mostly’ is doing a lot of heavy lifting. You’re likely to encounter #14 SAE or some common metric sizes. But relying on that assumption without checking can lead you down a rabbit hole of wrong-sized fasteners and wasted trips. My advice? Take a moment to identify what you actually need for your specific vehicle, and then invest in quality, stainless steel options. It’s the cheapest way to avoid future headaches and make sure your plate stays put.
Don’t just grab the cheapest pack of screws you see. Think about where they’re going – exposed to rain, salt, and sun. A few extra bucks for stainless steel now will save you from wrestling with rusted, seized fasteners later. It’s one of those small DIY wins that makes a big difference in the long run.
