Crop factor

The crop factor or focal length multiplier is the ratio between the size of the CCD sensor in your camera and the size of a typical 35mm film frame.

Usually CCDs are smaller, so the crop factor for a pocket camera can be around 6 and the crop factor for a DSLR is usually around 1.5. Some DSLRs have a 35mm size sensor so the factor for these is 1.

Alternatively it is easy to calculate as the ratio between the actual Focal Length and the 35mm equivalent focal length of the camera. Those two values can be found on the specification page of any digital camera where the CCD/CMOS size is harder to find

External link: The digital crop factor explained