lens size

[firstdigital]

how do i measure or find out what my lens size is? i am planning on purchasing a circular polarizer for my camera and have no idea as to what size filter i should be getting. can anyone point me " a newbie" in the right direction. thanks

1. Nikon 18-55mm f/3.5-5.6G ED AF-S DX Zoom-Nikkor Lens
2. Nikon 55-200mm f/4-5.6G ED AF-S DX Zoom-Nikkor Lens

[Prospero]

Both lenses have a filter size of 52mm
It is usually mentioned on the lens or the lens cap (at least, that is the case with my Sigma lenses).