The Most Common License Plate Screw Sizes
Most domestic (US-built) vehicles: 1/4-14 × 3/4 in self-tapping screw, or 1/4-20 × 3/4 in machine screw.
Most imports (Japanese, European, Korean): M6 × 1.0 mm machine screw, 16–20 mm long.
Best material: 304 or 316 marine-grade stainless steel — the only type that won’t leave rust streaks down your bumper.
You just picked up new plates or a fresh frame, walked into the hardware store, and hit a wall of generic bins labeled nothing useful. Nobody marks them “for license plates.” The difference between the right screw and the wrong one is whether you drive home done or strip a bumper insert you can’t easily replace.
This guide gives you the exact sizes for domestic and import vehicles, explains what the numbers on the package actually mean, and tells you which material to buy so you don’t repeat this job next year when the cheap dealership screws rust through.
Standard License Plate Screw Sizes
License plate mounting hardware splits into two systems depending on where your car was built. There is no single universal size, but there are dominant standards covering the vast majority of vehicles on US roads.
Left: SAE 1/4-20 screw used in most domestic US vehicles — wider diameter, coarser pitch. Right: M6 × 1.0 mm metric screw standard on most imports — slightly narrower, tighter threads. NOT interchangeable.
Domestic vs. Import Vehicle Quick-Reference Chart
Use this table to confirm the right car tag screw size before you buy. “Domestic” means assembled in North America for the North American market. Even some US brands use metric hardware depending on the generation and trim level — confirm with a visual check if in doubt.
| Vehicle Make / Region | Screw Type | Thread Size | Length | Market |
|---|---|---|---|---|
| Ford, Chevrolet, GMC, Dodge, Jeep (domestic models) | Self-tapping or machine | 1/4-14 or 1/4-20 | 3/4 in (19 mm) | Domestic |
| Toyota, Honda, Subaru, Mazda, Mitsubishi | Machine screw | M6 × 1.0 mm | 16–20 mm | Import |
| Hyundai, Kia, Genesis | Machine screw | M6 × 1.0 mm | 16–20 mm | Import |
| BMW, Mercedes-Benz, Audi, Volkswagen | Machine screw | M6 × 1.0 mm | 16–20 mm | Import |
| Volvo, Saab (legacy) | Machine screw | M6 × 1.0 mm | 16–20 mm | Import |
| Ford F-150, RAM (newer metric platforms) | Machine screw | M6 × 1.0 mm | 16 mm | Varies by Year |
| Tesla (all models) | Machine screw | M6 × 1.0 mm | 16 mm | Import Platform |
License Plate Screw Dimensions Explained
Hardware store packaging uses shorthand that looks confusing if you haven’t dealt with fasteners before. Here is what each number means for the two dominant systems.
Magnified thread comparison: SAE 1/4-20 has 8 threads per 10 mm of shaft (coarser). M6 × 1.0 mm has 10 threads per 10 mm (finer). The diameter difference is just 0.35 mm — why wrong-size screws appear to fit at first but strip the insert.
SAE (Imperial) Notation — e.g., 1/4-20 × 3/4 in
| Part of the Label | What It Means |
|---|---|
| 1/4 | Outer diameter of the screw shaft — 0.25 inches (6.35 mm) |
| 14 (or 20) | Threads per inch. 14 TPI = self-tapping (cuts its own thread). 20 TPI = machine screw (needs a pre-tapped insert). |
| 3/4 in | Total shank length, not including the head |
Metric Notation — e.g., M6 × 1.0 × 16 mm
| Part of the Label | What It Means |
|---|---|
| M6 | Metric thread, 6 mm nominal outer diameter |
| 1.0 | Thread pitch in millimeters — 1.0 mm between each thread crest. Standard coarse pitch for M6. |
| 16 mm | Shank length (16, 18, or 20 mm all work for most applications) |
Best Materials — Stop Rust Before It Starts
The zinc-plated screws most dealers install at the point of sale typically fail within 12–24 months in climates with road salt, humidity, or coastal air. They leave orange streaks on your bumper that look worse the longer they sit. The solution is paying about $2 more per screw upfront.
316 stainless steel lasts indefinitely in nearly all conditions. Zinc-plated steel — what most dealers use — typically fails within 18 months in salt-belt or coastal climates, leaving rust streaks on your bumper.
| Material | Rust Resistance | Best For | Cost (approx.) |
|---|---|---|---|
| 316 Stainless Steel | Excellent | Coastal, snow-belt, any climate | $1.50–$3.00 |
| 304 Stainless Steel | Very Good | Inland / dry climates | $0.80–$2.00 |
| Aluminum (anodized) | Good | Lightweight builds, cosmetic installs | $1.00–$2.50 |
| Zinc-plated carbon steel | Fair | Dry climates, short-term | $0.10–$0.40 |
| Unplated carbon steel | Poor | Avoid for exterior use | $0.05–$0.20 |
The recommendation is 304 SS for most drivers, and 316 SS for anyone near the coast or in states that salt roads heavily. The molybdenum content in 316 makes it significantly more resistant to chloride corrosion — the specific type caused by road salt and sea air — compared to 304.
Anti-Theft License Plate Screws
License plate theft has spiked in many US metro areas as stolen plates are used to disguise vehicles involved in toll evasion and other crimes. Anti-theft screws use a non-standard drive head that requires a special bit to remove. They are widely available in both M6 and 1/4-inch thread profiles.
Three anti-theft drive types compared. Pin-in-Torx is the most widely available and most secure — it requires a bit with a hollow center. One-way slots are simpler but easier to defeat with locking pliers.
Common anti-theft drive types include one-way slotted heads (spins freely counterclockwise), pin-in-Torx (requires a specialty bit with a center pin), and spanner heads. Standard Torx screws are not anti-theft — they are common enough that anyone with a T20 bit can remove them.
Installation Tips
Getting the screw in correctly takes about 90 seconds per hole when you do it right. Rushing costs you a stripped insert that takes considerably longer to fix.
The four rules that prevent a simple job from becoming a stripped-insert repair. Hand-threading first is the one most people skip — and the one that causes most cross-threading damage.
- 1 Confirm your thread type first — metric or SAE. Remove one existing screw and identify it before buying replacements.
- 2 Apply a thin coat of anti-seize compound to the threads. Do not use thread locker (Loctite) — it makes future removal extremely difficult.
- 3 Thread by hand for the first two full turns. If it resists before seating, stop — wrong thread or cross-threaded insert. Back out and start again.
- 4 Snug with a screwdriver, not a drill. License plate screws need only 4–6 inch-pounds of torque. A power drill strips plastic inserts immediately.
- 5 Leave washers in place (or add neoprene washers) if the frame requires them — they distribute load and prevent frame rattle at highway speeds.
Troubleshooting: Rusted & Spinning Screws
Three common failure scenarios and their fixes. Most stuck screws respond to penetrating oil within 30 minutes. A freely-spinning screw means the backing nut has detached — access from behind. A completely destroyed insert needs a rivet nut.
Screw head is stripped or won’t turn
Spray PB Blaster or WD-40 Specialist Penetrant directly onto the screw head and around the base. Wait a minimum of 10 minutes — 30 minutes is better for heavily corroded fasteners. Use a screwdriver with maximum contact area in the head slot and apply firm downward pressure while turning. If the head is completely destroyed, a screw extractor bit (reverse-threaded, available at any hardware store) grips the inside of stripped heads and backs them out.
Screw just spins — won’t come out
This means the backing nut insert behind the bumper is spinning with the screw. Access the back of the bumper fascia — on most vehicles this means reaching through the wheel well or from inside the trunk. Have a second person hold the nut with pliers or a wrench while you unscrew from the front. If access is impossible, use a hacksaw blade or oscillating tool to cut the screw shaft flush, then push the remnant through.
Thread insert is stripped out completely
Install a rivet nut (also called a nutsert) in the correct diameter. These expand behind the bumper panel when tightened and create a solid new threaded insert without needing access to the back side. Rivet nut kits are available at hardware stores and include the installation tool. Choose M6 or 1/4-20 to match your vehicle’s original thread standard.
