What Size Screws for a License Plate?

What size screw for a license plate: the two sizes

Plate screws are sold as both #14 (0.242 in) and 1/4 in (0.250 in); the two are nearly the same diameter. An M6 machine screw is a different kind of thread, made for metal threads.

How to tell which your car takes

1. Look in the hole with a flashlight.
   • White, black or tan plastic or nylon insert: use 1/4 in (#14) x 3/4 in self-tapping screws.
   • Metal threads or a nut behind the bumper or bracket: use M6-1.0.
   • Bare hole in a bracket: fit push-in nuts or nylon retainers first, then use the screw they're made for.
2. Measure the old screw if you have it. About 6.0 mm (0.236 in) with fine, even threads is M6-1.0. About 6.1–6.35 mm with coarse, widely spaced threads is a self-tapping 1/4 in or #14.
3. Try it by hand. An M6 screw in an M6 hole spins in by hand for several turns. If it binds after a turn, stop: the thread is wrong.

Common mistakes

• Forcing a self-tapping screw into a metal M6 thread. It damages the thread. Use an M6 screw.
• Driving an M6 machine screw into a plastic retainer. It may grip at first, but the retainer is made for a self-tapping screw.
• Re-using a stripped retainer. If the screw spins, replace the retainer; they're cheap.
• Going much longer than the old screw. Long screws can hit whatever sits behind the bumper. If you add a plate frame, go only as long as you need to get full grip.
• Plain steel screws on a car that sees road salt. Stainless or coated screws are easier to get out next time.

Not sure what you've got? Snap it

Snap the old screw next to a ruler and Mechy tells you the size, thread and length. If it's an M6 vs self-tapping call, try it by hand in the hole before you tighten. Identify a screw from a photo.