equivalent mm

[deutsh]

HI (((((if I have DX 18mm lens what the equivalent mm in FX (full frame))

 

[MTVision]

Around 27mm.

Edit: You just multiply the focal length by the crop factor which I believe is 1.5 for Nikon.

 

[Overread]

An lens of any focal length used on a crop sensor camera for Nikon will have 1.5 times the crop factor compared to 35mm (fullframe).

Thus an 18mm lens (be it a crop sensor only lens or a fullframe compatible lens) will give you the rough same angle of view as a 27mm lens would on a 35mm (fullframe) camera body.
Remember if you mount a crop sensor only lens to your fullframe camera body you'll still get the rough same angle of view (with the camera in its auto crop mode; if you disable this you might get a bit more frame coverage, but edge quality will suffer and you'll also likely get very dark corners - ie vignetting).