What is the lens filter thread of a Nikon D5100, 18-55 VR Kit lens?

And how does one check the lens filter thread? I need to buy some filters for my lens and wanted to confirm they'd be compatible before I bought them.

52mm

If you look at the front of a lens you will see xxΦ (ie. 52Φ, 58mmΦ, 72Φ, etcetera). This is the filter and cap size in millimeters for that particular lens.

You can check it at the front of the lens. Although I think it should be 58mm if I'm not wrong.

Http://keerok-photography.blogspot.com/2012/09/how-to-get-lens-filter-size.html

Yours should be 52mm.

52mm. It says so near the front of the lens.

52mm, 58mm, 72mm