What's the honda odyssey license plate screw size?

The Honda Odyssey license plate screw size is M6 thread and it is 1/2 of an inch long. This is what is designed to screw into the rear mounting plate that is on the back of the van. If You live in a state where You need to install a front license plate You can always use a M6 or 1/4" diameter self tapping screw to attach it to the front bumper around the middle. You could also install a frame into the front bumper that can hold it. The other option if You need to use a front plate is to use the towing eye location. There are brackets that can screw into the towing eye and let You install a plate without having to cut Your front bumper.